LIBRARY 

OF  THK 

UNIVERSITY  OF  CALIFORNIA. 

GIFT  OK 


Accession  ........  8.5.9.9.6  .....      -d'ass 


THE 


PRINCIPLES  OF. AGRICULTURE 


FOR 


COMMON  SCHOOLS 


BY 

I.  0.  WINSLOW,  A.M. 


NEW  YORK  •:•  CINCINNATI  •:•  CHICAGO 

AMERICAN    BOOK    COMPANY 


Copyright,  1890, 
BY  I.  O.  WINSLOW 


PREFACE. 


A  KNOWLEDGE  of  the  principles  of  agriculture, 
which  simply  means  a  knowledge  of  the  natural 
laws  and  principles  which'  underlie  rural  life  and  rural 
pursuits,  is  not  only  important  for  those  who  are  ac- 
tually engaged  in  the  pursuits  of  agriculture,  but  may 
in  general  be  regarded  as  an  important  element  in  the 
education  of  the  young. 

For  the  large  number  of  pupils  who  are  unable  to  pur- 
sue an  extended  academic  course  of  study,  the  natural 
sciences  should  not,  as  is  too  often  the  case,  be  wholly 
neglected. 

Although  the  time  of  the  school  course  may  not  admit 
of  a  thorough  mastery  of  any  one  of  these  sciences,  a 
selection  of  the  fundamental  and  elementary  principles 
of  each  may  be  consistently  and  profitably  presented. 

Education  of  this  kind,  impressing  upon  the  young  the 
mysteries  and  the  beauties  of  nature,  tends  to  increase 
the  fondness  for  our  native  soil,  and  to  develop  a  spirit 
of  genuine  patriotism. 

This  book  is  designed  primarily  for  use  in  the  public 
schools,  and  contains  no  difficulties  too  great  for  ordi- 
nary pupils  of  twelve  or  fourteen  years. 

(iii) 

85998 


iv  PREFACE. 

It  has  been  the  aim  to  observe  a  careful  analysis, 
separating  the  subjects  into  distinct  topics,  and  treat- 
ing each  briefly  and  concisely. 

Many  minor  and  subordinate  topics  have  been  pur- 
p-jsely  omitted.  The  experience  of  the  author  leads  him 
to  believe  that  a  thorough  knowledge  of  the  few  main 
points  of  a  subject  is  worth  more  to  the  pupil  than  a 
confused  idea  of  the  whole. 

There  are  many  problems  connected  with  the  subject 
of  agriculture  which  have  not  yet  been  solved,  and  many 
points  which  have  not  been .  definitely  settled.  These 
are  either  wholly  avoided  or  briefly  mentioned.  There 
is  enough  which  is  established  beyond  question  to  engage 
the  attention  of  beginners. 

The  first  chapters  of  the  work  contain  but  little  that 
belongs  peculiarly  to  the  science  of  agriculture,  but  they 
necessarily  form  the  foundation  of  that  science.  They 
comprise  some  of  the  leading  facts  and  principles  of 
chemistry,  natural  philosophy,  geology,  physical  geog- 
raphy, and  botany,  particularly  such  as  bear  directly 
upon  agriculture  and  rural  life. 

The  questions  at  the  end  of  each  chapter  are  inserted 
for  the  especial  purpose  of  assisting  such  teachers  as  are 
not  familiar  with  the  subjects,  and  do  not  feel  competent 
to  present  them.  As  the  work  is  arranged,  it  is  believed 
that  no  teacher  will  find  any  difficulty  in  understanding 
it  or  making  it  interesting. 

JUNE,  1891. 


CONTENTS. 


PAGES 
Suggestions  to  Teachers 6 

CHAPTER  I. 

The  Substances  of  the  Earth 7-25 

CHAPTER  II. 
Land  and  Water 26-40 

CHAPTER  IH. 
The  Atmosphere 41-53 

CHAPTER  IV. 
Plants 54-76 

CHAPTER  V. 
Fertilizers 77-99 

CHAPTER  VI. 
Cultivation 100-113 

CHAPTER  VII. 
Animals  114-144 


Glossary 145-146 

Index 147-152 


SUGGESTIONS  TO  TEACHERS. 


TRUE  teaching  requires  activity  and  original  work  on  the  part  of 
the  teacher.     To  rely  mainly  upon  the  text-book,  and  simply 
require  pupils  to  commit  to  memory  the  statements  of  the  text,  is  not 
teaching. 

The  aim  should  be  to  stimulate  in  the  minds  of  pupils  the  habit 
of  observing  and  thinking  for  themselves.  The  text  should  simply 
serve  as  a  guide,  or  starting  point,  for  the  work  of  the  class. 

This  is  particularly  true  of  subjects  related  to  the  natural  sciences, 
like  those  of  which  the  present  work  is  composed.  Many  topics  in 
the  text  are  necessarily  treated  with  brevity,  but  it  is  expected  that 
teachers  will  avail  themselves  of  the  opportunity  to  amplify  and  illus- 
trate them  with  familiar  examples. 

The  questions  at  the  end  of  each  chapter  may  be  used  for  review 
exercises  or  for  examinations.  They  may  also  be  used  in  daily  reci- 
tations, but  teachers  will  naturally  ask  many  similar  questions  of 
their  own. 

The  teaching  will  be  rendered  much  more  interesting  and  effectual 
by  the  free  use  of  object  lessons  and  simple  experiments.  Those 
who  are  accustomed  to  teach  the  natural  sciences  and  are  supplied 
with  apparatus  for  the  purpose,  need  no  suggestions  upon  this  point. 

The  outfit  of  a  chemical  laboratory  is  not  necessary,  however,  as 
the  ingenious  teacher  will  find  abundant  means  for  the  purpose 
within  reach.  Specimens  of  rocks,  soils,  and  plants  from  the  neigh- 
boring fields,  pots  of  soil  with  a  few  varieties  of  seeds  and  of  fer- 
tilizers, for  experiments  in  the  growth  of  plants,  a  small  quantity 
of  some  common  and  familiar  chemicals  purchased  for  a  few  cents  of 
the  nearest  apothecary,  and  a  small  microscope,  either  purchased  or 
borrowed  for  occasional  use,  are  among  the  means  available. 

It  will  serve  a  useful  purpose,  particularly  with  the  older  pupils, 
to  have  at  hand,  for  reference  and  comparison,  other  works  on  chem- 
istry, geology,  physical  geography,  botany,  and  agriculture. 

The  subject  is  naturally  interesting,  and,  if  wisely  presented,  can 
not  fail  to  afford  enjoyment  to  both  teacher  and  pupils,  and  to  yield 
satisfactory  results, 
(vi) 


THE  PRINCIPLES  OF  AGRICULTURE. 


CHAPTER  I. 

THE  SUBSTANCES  OF  THE  EARTH. 

Simple  Substances.  —  All  matter  of  which  the  earth,  the 
atmosphere,  and  all  plants  and  animals  are  composed 
consists  of  a  comparatively  small  number  of  simple  sub- 
stances or  elements. 

We  are  accustomed  to  think  of  the  ordinary  objects 
about  us  as  simple  in  their  nature,  and  as  composed  of 
but  one  kind  of  matter. 

This  is  true  of  a  few  substances,  like  pure  gold,  silver, 
and  iron  ;  but  the  greater  number  of  the  objects  with 
which  we  are  familiar  are  composed  of  several  simple 
substances  mixed  or  combined. 

Water  is  composed  of  two  gases.  Wood  may  be  di- 
vided into  ten  or  more  different  elements.  If  we  burn  a 
pile  of  wood  we  see  the  smoke,  we  know  that  there  are 
gases  escaping  which  we  cannot  see,  and  we  find  a  small 
quantity  of  ashes  remaining.  Neither  the  smoke,  the 
gases,  nor  the  ashes  appear  at  all  like  wood,  and  yet  we 
know  that  in  some  way  the  wood  has  been  transformed 
into  these  substances. 

(7) 


8  THE  PRINCIPLES  OF  AGRICULTURE. 

The  whole  number  of  elementary  substances  at  present 
known  is  from  sixty-five  to  seventy.  Some  of  them,  how- 
ever, are  very  rare. 

Only  fourteen  elements  are  generally  found  in  soil, 
plants,  and  animals.  Knowledge  of  these  is  of  impor- 
tance in  the  study  of  agriculture. 

They  are  as  follows  :  — 

Oxygen     .  .  .  O  Chlorine     .     .     .  Cl 

Nitrogen  .  .  .  N  Potassium  ......  K 

Hydrogen  .  .  H  Sodium  ....  Na 

Carbon      .  .  .  C  Calcium      .     .     .  Ca 

Silicon  ....  Si  Magnesium     .     .  Mg 

Sulphur     .  .  .  S  Aluminium      .     .  Al 

Phosphorus  .  .  P  Iron Fe 

These  names  are  used  so  often  that,  for  convenience, 
they  are  abbreviated,  each  being  represented  by  one  or 
two  letters.  The  abbreviations  are  called  symbols.  The 
symbols  for  potassium,  sodium,  and  iron  are  taken  from 
the  ancient  and  foreign  names  of  those  substances. 

Atoms.  —  All  matter  is  composed  of  minute  particles 
called  atoms.  These  are  so  small  that  they  have  never 
been  seen.  We  cannot  even  imagine  the  size  of  them. 
Millions  of  atoms  might  rest  upon  the  point  of  a  pin. 

The  belief  that  they  exist  is  embodied  in  what  is  called 
the  atomic  theory.  This  theory  is  believed  to  be  true, 
because  all  known  facts  are  consistent  with  it.  All  the 
facts  in  nature  with  which  we  are  acquainted,  and  the 
results  of  all  experiments  that  have  ever  been  tried,  are 
just  what  they  would  be  if  the  theory  were  true.  The 
fact  that  atoms  cannot  be  seen  is  no  reason  for  doubting 
their  existence.  We  are  limited  in  our  power  to  see 
and  understand.  As  we  are  unable  to  comprehend  the 
distance  to  the  sun,  and  the  immensity  of  space,  so,  on 


THE   SUBSTANCES  OF  THE  EARTH. 


9 


A  Drop  of  Water. 
(Magnified.) 


the  other  hand,  we  cannot  form  any  idea  of  the  minute- 
ness of  matter. 

Powerful  microscopes  have  revealed  forms  of  animal 
life  which  had  never  before  been  conceived  of.     It  is 
known  that  multitudes  of  liv- 
ing beings  may  occupy  a  single 
drop  of  water. 

An  atom  is  the  smallest 
particle  into  which  matter  can 
be  divided.  We  may  repeat- 
edly subdivide  a  piece  of  gold 
until  it  is  reduced  to  the 
thousand-millionth  part  of  an 
ounce,  and  yet  we  shall  be 
far  from  reaching  a  single 
atom.  If  it  were  possible  to 
continue  the  process  long  enough,  a  particle  would  finally 
be  obtained  which  could  no  longer  be  divided  or  changed 
in  any  respect. 

An  atom  of  oxygen  is  always  exactly  the  same,  whether 
it  forms  a  part  of  the  soil,  or  of  the  air,  or  enters  into  the 
structure  of  a  plant  or  an  animal. 

An  atom  is  represented  by  the  symbol  which  is  used 
to  denote  the  kind  of  substance.  The  symbol  0  may 
denote  a  quantity  of  oxygen  in  general,  or  an  atom  of 
oxygen.  A  number  of  atoms  is  indicated  by  a  figure 
written  below,  and  to  the  right.  02  denotes  two  atoms 
of  oxygen,  HG  six  atoms  of  hydrogen. 

Molecules.  —  Atoms  do  not  generally  exist  alone.  They 
possess  a  force  of  attraction  which  causes  them  to  unite 
with  other  atoms,  either  of  the  same  kind  or  of  a  differ- 
ent kind. 

This  force  is  called  chemical  affinity.    It  causes  atoms  to 


10  THE  PRINCIPLES  OF  AGRICULTURE. 

unite  in  regular  groups.  A  group  of  this  kind  is  called 
a  molecule,  which  means  a  little  mass. 

Two  atoms  of  hydrogen  uniting  with  one  of  oxygen 
form  a  molecule  of  water.  Twelve  atoms  of  carbon, 
twenty-two  atoms  of  hydrogen,  and  eleven  atoms  of 
oxygen,  produce  a  molecule  of  sugar. 

Molecules,  though  larger  than  atoms,  are  yet  too  small 
to  be  seen. 

A  molecule  is  represented  by  writing  together  the 
symbols  of  the  different  kinds  of  atoms  of  which  it  is 
composed,  giving  the  number  of  atoms  of  each  kind. 
The  expression  H20  represents  either  a  molecule  of 
water  or  water  in  general.  H2S04  denotes  sulphuric 
acid,  and  indicates  that  in  a  molecule  of  the  acid  there 
are  united  two  atoms  of  hydrogen,  one  of  sulphur,  and 
four  of  oxygen. 

When  more  than  one  molecule  is  to  be  represented, 
the  number  is  indicated  by  a  figure  prefixed.  2  C02 
represents  two  molecules  of  carbonic  acid. 

In  all  molecules  of  the  same  substance  the  atoms  are 
supposed  to  maintain  a  uniform  order  of  arrangement. 

They  always  hold  regular  positions  with  respect  to  each 
other.  The  positions  depend  upon  the  relative  degree 
of  attraction  which  the  atoms  have  for  each  other. 

The  arrangements  are  supposed  to  be  somewhat  like 

the  following :  — 

H 

Na-Cl.         H-O-H.  H-N-H.          H-0-Ca-O-H. 

(Salt.)  (Water.)  (Ammonia.)  (Slaked  Lime.) 

The  Nature  of  Matter,  —  The  nature  of  any  substance 
depends  upon  the  nature  of  the  molecules  of  which  it  is 
composed.  It  may  be  entirely  different  from  the  sub- 
stances whose  atoms  unite  to  form  the  molecule. 


THE  SUBSTANCES  OF  THE  EARTH.  11 

Hydrogen  and  nitrogen  are  both  odorless,  but  when 
united  they  form  ammonia  (NH3)  which  is  noted  for  its 
strong  odor.  Chlorine  alone  is  poisonous,  but  with  sodium 
it  forms  common  salt  (NaCl).  The  great  variety  of  dif- 
ferent kinds  of  matter  is  produced  by  the  great  number 
of  possible  combinations  of  atoms  of  the  elementary 
substances. 

Chemical  Action.  —  Molecules  are  the  smallest  particles 
into  which  a  substance  can  be  divided  without  changing 
its  nature.  Whatever  change  is  wrought  upon  matter, 
its  real  nature  remains  the  same  so  long  as  its  individual 
molecules  are  not  broken  up. 

A  substance  may  be  melted,  or  converted  into  a  gas,  or 
mixed  with  some  other  substance,  and  yet  it  is  the  same 
substance  ;  but  if  its  molecules  are  divided  into  their  sep- 
arate atoms,  and  these  unite  again  with  other  atoms  in 
different  combinations,  it  is  no  longer  the  same. 

The  force  which  divides  molecules  into  their  separate 
atoms,  and  permits  them  to  form  other  combinations,  so 
as  to  produce  new  substances,  is  called  chemical  force,  or 
the  chemical  action  of  one  substance  upon  another. 

When  two  molecules  of  different  kinds  are  brought  to- 
gether, if  some  of  the  atoms  of  one  are  more  strongly 
attracted  by  atoms  in  the  other  than  by  neighboring  atoms 
in  their  own  molecule,  one  or  both  of  the  molecules  will 
be  broken  up  and  new  molecules  will  be  formed. 

When  water  is  poured  upon  quicklime,  the  atoms 
of  the  water  molecule  unite  with  those  of  the  lime  mole- 
cule, forming  molecules  of  a  new  substance,  or  slaked 
lime. 

When  some  of  the  atoms  are  not  needed  in  making  up 
the  new  molecule  they  are  set  free.  If  pieces  of  zinc  are 
placed  in  hydrochloric  acid,  the  chlorine  of  the  acid  will 


12  THE  PRINCIPLES  OF  AGRICULTURE. 

unite  with  the  zinc,  and  the  atoms  of  hydrogen  unite  with 
one  another,  forming  molecules  of  free  hydrogen. 

Chemical  force  sometimes  changes  the  nature  of  a 
substance  by  simply  changing  the  arrangement  of  atoms 
in  its  molecules.  The  molecules  of  cane  sugar,  and 
those  of  gum  arabic,  for  instance,  contain  exactly  the 
same  number  of  corresponding  atoms  (C12H220n).  There 
are  other  instances  in  which  the  same  is  true.  The  only 
explanation  of  this  is  that  the  atoms  must  occupy  different 
positions  with  respect  to  one  another  in  the  molecules  of 
the  different  substances. 

Chemical  Equations.  —  The  action  of  chemical  force  in 
breaking  up  molecules  of  different  kinds  when  they  are 
brought  together,  and  forming  new  molecules,  is  repre- 
sented by  an  equation. 

In  the  case  of  water  and  lime  the  equation  is : 

CaO  +  H20  =  Ca02H2. 

(Lime.)         (Water.)      (Slaked  Lime.) 

For  zinc  and  hydrochloric  acid  it  would  be  : 
2.HC1   +    Zn    =    ZnCla    +     H2. 

(Acid.)  (Zinc.)    (Zinc  Chloride.)    (Hydrogen.) 

In  the  latter  case  it  requires  two  molecules  of  the  acid 
to  combine  with  one  of  zinc,  forming  a  molecule  of  zinc 
chloride  and  liberating  two  atoms  of  hydrogen. 

Acids,  Bases,  and  Salts.  —  There  are  three  general  classes 
of  substances  with  which  we  must  become  acquainted 
in  order  to  understand  the  chemical  principles  of  agri- 
culture. 

They  are  called  acids,  bases,  and  salts. 

The  acids  are  a  class  of  substances  which  generally 
have  a  sour  taste.  Vinegar  contains  acetic  acid. 

Some  of  the  more  common  acids  arc :  sulphuric  acid 


THE   SUBSTANCES  OF  THE  EARTH.  13 

(H2S04),  muriatic  or  hydrochloric  acid  (HC1),  phospho- 
ric acid  (H3P04),  silicic  acid  (H4Si04),  carbonic  acid 
(CO,),  nitric  acid  (HN08),  etc. 

Bases  are  a  class  of  substances  whose  nature  is  very 
different  from  that  of  acids.  A  portion  of  them  are 
called  alkalies,  or  alkaline  sutstances,  and  have  a  hot, 
sharp  taste. 

Some  of  the  bases  are  potash  (K20),  sodium  (Na), 
lime  (CaO),  magnesia  (MgO),  oxide  of  iron  or  iron  rust 
(FeO),  etc. 

Acids  and  bases  have  a  strong  attraction  for  one  an- 
other, and  when  united  form  a  class  of  substances  called 
salts.  They  are  so  named  because  many  of  them  have  a 
taste  similar  to  that  of  common  salt. 

They  are  called  sulphates,  chlorates,  phosphates, 
etc.,  as  chlorate  of  potash  (KC103),  phosphate  of  lime 
(CaOP205),  nitrate  of  soda  (NaN03),  etc. 

Gypsum,  or  land  plaster,  is  sulphate  of  lime  and  water. 
It  is  the  result  of  a  combination  of  sulphuric  acid  and 
quicklime : 

H2S04  +  CaO  =  (CaS04  +  H20). 

Phosphate  of  lime  is  produced  by  a  union  of  phosphoric 
acid  and  quicklime : 

2  H3P04  +  CaO  =  CaOP205  +  3  H20. 

If  a  feather  is  dipped  in  hydrochloric  acid  and  held 
over  an  open  bottle  of  ammonia,  the  ammonia,  escaping 
by  evaporation,  will  unite  with  the  acid  and  form  a  white 
powder  upon  the  feather,  called  ammonic  chloride : 

NH8  +  HC1  =  NH4C1. 

When  the  two  parts  of  a  rochelle  powder  are  dissolved 
and  poured  together,  the  acid  of  the  one  unites  with  the 
base  of  the  other,  producing  a  salt,  which  remains  dis- 


14  THE  PRINCIPLES  OF  AGRICULTURE. 

solved  in  the  water;  and  carbonic  acid,  which  escapes  in 
the  form  of  a  gas,  causing  the  effervescence. 

Cohesion  and  Adhesion.  —  As  atoms  have  attractions 
which  cause  them  to  unite  in  molecules,  so  the  molecules 
themselves  have  similar  attractions  for  one  another. 

When  the  attraction  is  between  molecules  of  the  same 
kind,  it  is  called  cohesion ;  when  between  molecules  of 
different  kinds,  it  is  called  adhesion. 

Molecules  of  water  have  an  attraction  of  cohesion  for 
one  another,  but  the  adhesion  between  water  and  glass  is 
sufficient  to  overcome  this,  and  to  cause  a  piece  of  glass 
to  be  moistened  when  dipped  in  water.  On  the  other 
hand,  an  oily  stick  will  not  be  moistened  by  water,  be- 
cause the  cohesion  in  water  is  stronger  than  the  adhesion 
between  water  and  oil. 

The  adhesive  attraction  of  water  for  gases  causes  the 
moisture  of  the  atmosphere  to  absorb  impurities  and 
bring  them  down  with  the  rain. 

The  attraction  of  charcoal  for  various  substances 
renders  it  useful  as  a  filter  for  cleansing  water,  refining 
sugar,  etc. 

In  order  that  the  forces  of  cohesion  and  adhesion  may 
act,  it  is  necessary  to  bring  the  molecules  very  near  to 
one  another.  In  breaking  a  piece  of  iron,  we  exert  a 
force  upon  it  sufficient  to  pull  its  molecules  so  far  apart 
that  the  force  of  cohesion  no  longer  acts. 

In  order  to  weld  the  separated  parts  it  is  necessary  to 
heat  them  until  their  molecules  will  move  more  easily, 
and  then  beat  them  together  by  hammering  until  the 
molecules  are  again  brought  within  the  range  of  cohesive 
force. 

In  stretching  a  piece  of  rubber,  we  draw  the  molecules 
farther  and  farther  apart,  until  finally  the  force  applied 


THE   SUBSTANCES  OF  THE  EARTH. 


15 


is  sufficient  to  overcome  the  force  of  cohesion  by  which 
the  molecules  are  attracted  to  one  another,  and  they  are 
separated  or  the  rubber  is  broken. 

The  Porosity  of  Matter.  —  All  matter  is  more  or  less 
porous.  This  is  not  only  true  of  loose  substances  like 
soil,  but  also  of  more  solid  substances,  like  wood  and 
iron.  The  pores  in  the  latter  are,  like  atoms  and  mole- 
cules, too  small  to  be  seen. 

n  c  w 


Cross-section  of  Wood,  magnified,  showing  Pores. 
£,  the  bark ;  C,  the  cambium  layer;  W,  wood. 

It  is  believed  that  neither  atoms  nor  molecules  ever 
remain  in  absolute  contact  with  each  other,  but  that  there 
are  always  spaces  between  them.  Through  these  spaces 
atoms  and  molecules  of  other  substances  are  able  to  pass. 

A  certain  amount  of  salt  and  sugar  may  be  dissolved 
in  water  without  increasing  the  volume  of  water.  The 
molecules  of  salt  and  'sugar  occupy  the  vacant  spaces 
between  the  molecules  of  water. 

Under  heavy  pressure  water  has  been  forced  through 
the  pores  of  iron.  A  piece  of  iron  may  be  made  smaller 
by  hammering.  Its  molecules  are  then  driven  nearer 
together. 

A  bottle  filled  with  gas  will  hold  as  much  of  another 
kind  of  gas  as  if  it  were  empty. 


16  THE  PRINCIPLES  OF  AGRICULTURE. 

Solids,  Liquids,  and  Gases.  —  Matter  exists  in  one  of  three 
states :  either  as  a  solid,  a  liquid,  or  a  gas.  The  same 
substance  may  assume  one  of  these  forms  at  one  time, 
and  another  at  another  time. 

The  state  is  supposed  to  depend  upon  the  degree  of 
attraction  by  which  its  molecules  are  bound  together. 

When  they  are  firmly  united,  the  substance  is  a  solid. 
When  the  force  that  binds  them  is  weaker,  allowing  them 
to  move  freely  upon  one  another,  it  becomes  a  liquid. 
When  the  force  is  entirely  overcome,  it  becomes  a  vapor 
or  gas.  The  molecules  then  fly  apart,  tending  to  occupy 
as  much  space  as  possible. 

The  state  of  a  substance  is  partly  dependent  upon  the 
temperature. 

Heat  tends  to  overcome  the  attraction,  and  so  to  change 
a  substance  to  the  liquid  or  gaseous  form.  A  moderate 
amount  of  heat  will  change  a  block  of  ice,  first  to  water 
and  then  to  vapor.  A  higher  temperature  will  produce 
a  similar  effect  upon  other  solids. 

Heat,  by  overcoming  the  force  that  draws  molecules 
together,  increases  the  distance  between  them,  and  so 
increases  the  space  which  they  occupy  and  the  size  of 
the  body.  So,  on  the  other  hand,  a  low  temperature  al- 
lows the  molecules  to  come  nearer  together,  and  renders 
the  body  smaller. 

There  are  a  few  exceptions  to  the  general  rule  that 
heat  expands  and  cold  contracts.  When  water,  is  cooled 
enough  to  freeze,  or  become  a  solid,  it  is  crystallized  ; 
that  is  to  say,  its  molecules  arrange  themselves  in  cer- 
tain forms  which  require  more  space  than  if  they  were 
packed  closely  together.  The  same  is  true  of  a  few  other 
substances  when  changing  from  the  liquid  to  the  solid 
state. 


TIIE   SUBSTANCES  OF  THE  EARTH.  17 

The  expansive  force  of  water  in  freezing,  or  crystal- 
lising, is  very  great.  A  pitcher  iilled  with  water,  and 
allowed  to  freeze,  is  sure  to  be  broken.  The  moisture  of 
the  soil  in  freezing  beneath  a  building  lifts  it  perceptibly 
every  winter. 

Siiowflakes  illustrate  the  tendency  of  freezing  water 
to  crystallize.  When  examined  with  a  microscope,  they 
present  a  great  variety  of  regular  forms  whose  beauty 
and  accuracy  it  would  be  difficult  to  imitate. 


Snow  Crystals. 

Other  substances,  like  sugar,  salt,  and  alum,  show  the 
same  tendency.  When  these  are  dissolved  in  water,  as 
their  molecules  slowly  come  together  again  by  the  evap- 
oration of  the  water,  they  tend  to  arrange  themselves  in 
regular  forms. 

Organic  and   Inorganic  Matter.  —  Matter   is  sometimes 
divided  into  two  classes  :  organic  and  inorganic. 
WINS.  AGR.—  2 


18  THE  PRINCIPLES  OF  AGRICULTURE. 

Organic  substances  are  those  which  have  been  con- 
verted into  living  organisms  ;  or,  in  other  words,  which 
either  form  or  have  formed  a  part  of  the  bodies  of 
plants  and  animals.  They  are  produced  by  the  processes 
of  life.  All  other  matter  is  called  inorganic. 

When  organic  matter  is  burned  or  decays,  it  returns 
again  to  an  inorganic  condition. 

Pieces  of  stone  or  iron,  for  instance,  are  not  organic, 
because  they  have  no  organs  such  as  exist  in  anything 
which  has  life.  On  the  other  hand,  wood,  hay,  flesh, 
and  bones  are  examples  of  organic  matter,  since  they 
have  been  produced  by  the  growth  of  living  plants  and 
animals,  and  retain  the  same  matter  and  the  same  form 
which  they  had  when  in  a  living  state.  Soil  may  be 
partly  organic  and  partly  inorganic,  since  it  not  only 
contains  mineral  matter,  but  also  vegetable  and  animal 
matter,  left  by  the  death  of  plants  and  animals,  which 
has  not  yet  become  so  far  changed  as  to  lose  its  organic 
condition. 

Organic  substances  have  never  been  produced  by  arti- 
ficial means.  For  articles  of  food,  —  fruit,  vegetables, 
and  meat,  —  as  well  as  for  the  materials  used  for  cloth- 
ing,—  cotton,  wool,  linen,  and  silk,  — the  world  must 
depend  upon  nature's  processes  in  agriculture. 

All  attempts  to  imitate  nature  by  producing  these  sub- 
stances have  failed. 

Combustible  and  Incombustible  Matter.  —  When  any  sub- 
stance is  burned,  some  of  its  elements  escape  into  the 
atmosphere  in  the  form  of  gases  and  floating  particles, 
and  the  remainder  become  ashes.  The  carbon  unites 
with  the  oxygen  of  the  air,  and  escapes  as  carbonic  acid 
gas.  Some  of  the  nitrogen  is  converted  into  ammonia 
gas.  The  water  is  converted  into  vapor. 


THE   SUBSTANCES  OF  THE 


The  elements  which  escape  include  the  carbon,  hydro- 
gen, oxygen,  and  nitrogen,  and  sometimes  the  sulphur. 
The  remaining  elements  are  found  in  the  ashes.  The 
former  are  called  combustible  or  volatile,  and  the  latter 
incombustible  or  fixed. 

The  following  is  a  brief  description  of  the  more  com- 
mon elements  :  — 

Oxygen  is  the  most  common  and  interesting  of  the 
elements.  It  forms  about  one  half  of  the  solid  parts  of 
the  earth,  eight  ninths,  by  weight,  of  all  water,  and  one 
fifth  of  the  air.  It  has  powerful  attractions  for  many 
other  elements.  The  substances  formed  by  its  union 
with  these  are  generally  called  oxides.  Water  (H20) 
is  sometimes  called  hydric  oxide.  Lime  (CaO)  is  cal- 
cic oxide;  iron  rust  (FeO),  ferric  oxide.  There  are 
three  familiar  processes  in  nature  in  which  oxygen 
takes  a  leading  part:  — 

1.  Combustion.  —  The  ordinary  process  of  burning,  or 
combustion,  consists  of  the  union  of  the  oxygen  of  'the 
air  with  carbon  and  some  other  elements  of  the  fucL 
This  union  with  carbon  produces  a  gas  (C02)   called 
carbon  dioxide,  or  carbonic  acid  gas. 

Heat  is  a  result  of  the  union.  It  is  regarded  as  a 
kind  of  force.  The  force  or  clash  with  which  atoms 
come  together  in  burning  is  converted  into  another  kind 
of  force  called  heat.  The  degree  of  heat  depends  upon 
the  rapidity  of  the  process.  A  draft  through  a  fire  in- 
creases the  heat,  because  it  furnishes  a  larger  supply  of 
oxygen. 

2.  Oxidation.  —  In  the  rusting  of  metals,  and  the  de- 
cay of  wood,  a  process  is  going  on  precisely  similar  to 
that  of  burning,  except  that  it  is  much  slower.     New 
combinations  are  formed,  and  the  same  amount  of  heat 


20  THE  PRINCIPLES  OF  AGRICULTURE. 

is  produced  as  if  the  iron  or  wood  were  burned,  or  oxi- 
dized more  rapidly.  The  process  is  so  slow  that  the 
heat  is  not  noticeable. 

The  decomposition  and  decay  of  all  substances,  in  gen- 
eral, is  largely  a  process  of  oxidation.  Articles  of  food 
are  preserved  from  decay  by  separation  from  the  oxygen 
of  the  air.  The  decay  of  soft  vegetable  substance,  as  well 
as  the  crumbling  of  the  hardest  rock,  shows  the  power 
of  oxygen  in  transforming  the  products  of  nature. 

3.  Respiration. —  Respiration  or  breathing  in  animals 
is  similar  to  combustion  and  oxidation.  The  oxygen  of 
the  air,  taken  into  the  lungs,  enters  the  blood,  where  it 
unites  with  carbon.  The  carbonic  acid  gas  thus  pro- 
duced escapes  with  the  breath  into  the  atmosphere. 

The  heat  which  results  from  this  union  serves  to  keep 
up  the  temperature  of  the  body  of  the  animal.  The 
amount  of  heat  per  day  produced  in  the  system  of  a  man 
by  breathing  is  about  equal  to  that  obtained  by  burning 
a  pound  of  coal. 

Plants  breathe  to  a  slight  extent,  taking  in  oxygen 
through  the  pores  of  their  leaves,  and  giving  off  carbonic 
«,cid  gas. 

Hydrogen  is  the  lightest  substance  known.  It  weighs 
only  one  sixteenth  as  much  as  oxygen.  It  combines 
most  readily  with  oxygen  and  chlorine.  When  burned 
or  combined  with  oxygen,  it  forms  water.  It  is  an  es- 
sential part  of  plants  and  animals.  It  is  produced  by  the 
decay  of  animal  and  vegetable  matter,  or  from  molecules 
of  water,  by  separating  it  from  the  atoms  of  oxygen, 

Nitrogen,  in  a  free  state,  forms  four  fifths  of  the  air. 
It  is  an  odorless  and  harmless  gas.  Its  purpose  in  the 
air  seems  to  be  to  dilute  the  oxygen  with  which  it  is 
mixed  and  diminish  its  force. 


THE   SUBSTANCES  OF  THE   EARTH.  21 

It  forms  an  essential  part  of  plants  and  animals,  and 
is  of  great  importance  for  agricultural  purposes.  Its 
force  of  attraction  for  other  elements  is  very  weak.  This 
fact  increases  the  difficulty  of  retaining  it  in  permanent 
forms.  It  is  the  most  expensive  part  of  fertilizers. 
With  hydrogen  it  forms  ammonia  (NH3)  ;  with  hydrogen 
and  oxygen,  nitric  acid  (HN03).  These  are  the  two 
forms  in  which  nitrogen  most  commonly  becomes  a 
source  of  fertility,  and  of  importance  in  agriculture. 

Carbon  is  found  in  nature  in  three  forms  :  as  charcoal 
and  similar  substances ;  as  graphite,  which  is  used  in 
making  lead  pencils  ;  and  as  diamonds,  which  are  simply 
crystallized  carbon. 

It  forms  a  large  part  of  all  animal  and  vegetable  sub- 
stances. Coal,  wood,  and  woody  substances  are  largely 
composed  of  it.  It  is  the  element  which  gives  value  to 
substances  used  as  fuel. 

Charcoal,  which  is  largely  composed  of  free  carbon,  is 
produced  by  burning  wood  in  a  partially  smothered  fire. 
The  process  releases  the  carbon  from  other  elements 
with  which  it  is  combined,  and  retains  it  by  excluding 
the  oxygen  of  the  air,  with  which  it  would  otherwise 
unite  and  escape  as  carbonic  acid  gas. 

If  a  piece  of  wood  is  placed  in  sulphuric  acid  and  al- 
lowed to  remain  for  some  time  it  becomes  black.  The 
acid  removes  the  other  elements  of  the  wood  and  leaves 
the  carbon. 

If  a  piece  of  glass  is  held  over  the  flame  of  a  candle  it 
becomes  "  smoked,"  or  covered  with  minute  particles  of 
carbon,  which  escape  faster  than  they  can  be  consumed. 

All  plants  contain  a  large  proportion  of  carbon.  In 
cotton  fiber  it  is  almost  pure.  Sugar,  which  is  a  product 
of  plants,  is  forty-two  per  cent,  carbon,  by  weight. 


22  THE  PRINCIPLES   OF  AGRICULTURE. 

Silicon  is  the  most  abundant  solid  substance  known. 
It  forms  about  one  fourth  of  the  solid  parts  of  the  earth. 
It  is  commonly  combined  with  oxygen  in  the  form  of  sil- 
ica (Si02).  Quartz  rock  is  a  variety  of  silica.  It  forms  a 
large  part  of  granite  rock,  sandstone,  and  common  sand. 
It  serves,  like  an  acid,  to  unite  with  bases,  forming  what 
are  called  silicates.  Common  glass  is  a  mixture  of  dif- 
ferent silicates.  Clay  is  chiefly  composed  of  silicate  of 
alumina. 

Silica  is  found  in  plants,  particularly  in  the  grasses. 
It  gives  to  the  stalks  and  branches  greater  firmness  and 
hardness. 

Sulphur  is  a  familiar  substance,  commonly  known  as 
brimstone,  or  flowers  of  sulphur.  With  hydrogen  and 
oxygen  it  forms  sulphuric  acid  (H2S04),  one  of  the  most 
common  acids.  This  acid  forms  a  great  variety  of  useful 
salts,  as  sulphate  of  potash  (K2S04),  sulphate  of  lime 
(CaS04),  etc. 

Sulphur  is  always  found  in  plants  and  animals.  The 
strong  flavor  of  such  vegetables  as  turnips  and -onions  is 
due  to  the  presence  of  sulphur. 

Phosphorus  is  a  soft,  yellow  substance,  which  unites 
with  the  oxygen  of  the  air  and  takes  fire  so  easily  that 
it  can  only  be  kept  under  water.  It  is  used  in  manu- 
facturing matches.  It  combines  with  hydrogen  and 
oxygen,  forming  phosphoric  acid  (H3P04),  a  substance 
of  great  importance  in  fertilizers.  It  forms  about  ten 
per  cent,  of  the  bones  of  animals,  in  the  form  of  calcium 
phosphate. 

Chlorine  is  a  gas  which  is  found  only  in  combination 
with  other  elements.  With- hydrogen  it  produces  hydro- 
chloric or  muriatic  acid  (HC1)  ;  with  sodium,  sodium 
chloride  or  common  salt  (NaCl). 


THE   SUBSTANCES  OF  THE  EARTH.  23 

Potassium  is  a  soft,  light  substance,  whose  affinity  for 
oxygen  is  so  strong  that  it  can  only  be  kept  pure  in  some 
substance  containing  no  oxygen.  When  placed  upon  a 
piece  of  ice  it  burns  freely. 

With  oxygen  it  forms  potash  (K20),  and  with  oxygen 
and  hydrogen  caustic  potash  ^KOH).  Potash  unites 
with  acids  producing  a  variety  of  salts  of  potash,  as  chlo- 
rate of  potash  (KC103),  sulphate  of  potash  (K2S04),  etc. 

Sodium  is  somewhat  similar  to  potassium.  It  forms  a 
great  variety  of  salts,  of  which  common  salt  (NaCl)  is  a 
familiar  example.  Caustic  soda  is  prepared  in  large 
quantities  for  manufacturing  soap. 

Calcium  is  a  common  substance,  found  in  combination 
with  other  elements,  from  which  it  is  not  easily  separated. 
In  limestone  and  marble  it  is  united  with  carbonic  acid, 
forming  calcium  carbonate  (CaC03). 

Compounds  of  calcium  constitute  a  large  part  of  the 
shells  of  clams,  oysters,  and  other  shell-fish,  and  also  of 
the  bones  of  all  animals. 

Magnesium  is  a  metal  found  in  some  rocks.  The  pure 
metal  burns  brilliantly,  and  is  sometimes  used  for  illu- 
minating purposes  when  a  very  strong  light  is  required. 
It  is  found  to  some  extent  in  plants  and  animals.  With 
oxygen  it  forms  magnesia  (MgO). 

Aluminium  is  somewhat  similar  to  magnesium.  It 
resembles  silver  in  appearance.  It  is  used  to  a  small 
extent  in  making  jewelry  and  ornamental  work.  The 
sapphire  and  ruby  are  beautiful  forms  of  alumina.  It 
exists  largely  in  common  clay  in  combination  with  silica. 

Iron  is  found  in  many  parts  of  the  earth  in  the  form  of 
ore,  which  is  purified  and  used  for  manufacturing  pur- 
poses. It  exists  to  some  extent  in  all  soils.  It  gives 
clayey  soils  their  dark  brown  color. 


24  THE  PRINCIPLES  Otf  AGRICULTURE. 


QUESTIONS. 

How  many  different  elementary  substances  are  there  in  the  earth? 
Name  those  which  are  most  common.  Name  as  many  others  as 
you  can  think  of.  What  is  meant  by  the  symbol  of  a  substance  V 
Name  the  symbols  of  the  most  common  substances. 

What  is  an  atom?  Have  atoms  ever  been  seen?  How  do  we  know 
that  they  exist?  How  are  atoms  represented?  Give  an  idea 
of  the  size  of  an  atom.  Can  an  atom  be  divided?  Can  it  be 
destroyed  ? 

What  is  a  molecule  ?  What  causes  atoms  to  form  molecules  ?  How 
is  a  molecule  represented  ?  How  are  the  atoms  of  a  molecule 
arranged  ? 

Upon  what  does  the  nature  of  matter  depend  ?  Must  all  substances 
composed  of  carbon,  hydrogen,  and  oxygen  be  alike?  Can  the 
molecules  of  a  body  be  broken  or  divided  ?  How  can  this  be  done  ? 
What  effect  does  this  have  upon  a  body  ?  What  would  be  the 
effect  of  making  a  different  arrangement  of  the  atoms  in  the  mole- 
cules of  a  substance  ? 

What  is  chemical  action  ?  Give  an  example  of  chemical  action,  and 
explain  it. 

What  are  acids  ?    Bases  ?     Salts  ?    Name  some  of  each. 

Give  a  chemical  equation  showing  how  bases  are  formed. 

What  is  cohesion  ?  What  is  adhesion  ?  Why  does  your  hand  become 
wet  when  dipped  in  water  ?  Why  are  the  feet  kept  dry  by  greas- 
ing the  boots?  How  is  water  purified  by  leaching  through  char- 
coal ?  Why  are  not  two  pieces  of  wood  touching  each  other  held 
together  by  cohesion  ? 

How  many  porous  substances  are  there?  How  do  we  know  that  iron 
is  porous  ?  Why  can  salt  be  added  to  a  glass  full  of  water  without 
causing  it  to  run  over  ?  Why  may  two  gases  appear  to  occupy  the 
same  space  at  the  same  time  ? 

Explain  the  difference  beween  solids,  liquids,  and  gases?  Why  is  a 
substance  melted  by  heating  it?  How  is  it  that  heat  expands  and 
cold  contracts?  Why  does  water  expand  in  freezing? 

WThat  is  the  difference  between  organic  and  inorganic  matter  ?  Is 
hay  organic  or  inorganic?  A  potato?  Water?  Milk?  Sand? 
Ordinary  soil? 


THE  SUBSTANCES  OF  THE  EARTH.  25 

Explain  the  difference  between  combustible  and  incombustible  matter. 
Mention  some  common  substances  which  are  partly  combustible. 
Mention  some  which  are  entirely  combustible.  Name  some  that 
are  entirely  incombustible. 

How  much  oxygen  is  there  in  the  earth?  What  is  an  oxide?  Ex- 
plain the  process  of  burning.  What  js  heat  ?  Why  does  a  fire  burn 
better  in  a  draft  of  air  ?  Why  has  decayed  wood  lost  a  part  of  its 
value  for  fuel  ?  Why  do  we  seal  fruit  to  preserve  it  ?  How  does 
breathing  keep  the  body  warm  ? 

What  are  the  peculiarities  of  hydrogen  ?  Why  is  water  produced  by 
burning  hydrogen  ?  Where  is  nitrogen  to  be  found  ?  Why  is  it 
so  difficult  to  obtain  it  for  practical  purposes  ? 

Name  some  objects  that  contain  carbon.  What  proportion  of  the 
earth  is  silicon  ?  Name  some  forms  in  which  it  is  found.  Name 
some  of  the  uses  of  sulphur.  Describe  phosphorus.  Name  some 
useful  forms  of  chlorine. 

Describe  potassium.  Name  some  of  the  salts  of  potash.  Mention 
some  useful  forms  of  sodium  AVhere  is  calcium  found?  How 
may  ma.gnesium  be  distinguished  ?  Name  some  forms  of  aluminium. 
Where  does  iron  exist? 


CHAPTER  II. 

LAND  AND  WATER. 

The  Former  Condition  of  the  Earth.  —  The  earth  has  not 
always  been  as  it  now  is,  but  has  been  gradually  chang- 
ing through  long  periods  of  years.  It  is  believed  that 
it  was  once  very  hot,  —  so  hot  that  all  the  solid  sub- 
stances now  upon  it  were  melted,  or  converted  into  gases. 
As  it  gradually  cooled  upon  the  outside,  some  of  these 
liquids  and  gases  became  solid,  and  formed  a  crust  upon 
.the  surface.  It  is  believed  that  the  interior  of  the  earth 
remains  to  the  present  day  in  a  very  hot  condition. 
There  are  several  indications  of  this :  — 

1.  In  descending  into  the  earth,  after  passing  below 
the  effect  of  the  sun's  heat,  the  temperature  becomes 
higher  the  farther  we  descend. 

2.  Earthquakes  are,  in  some  way,  due  to  movements 
of  the  melted  substances  or  gases,  or  of  the  crust  above 
them. 

3.  Some  of  the  hot  liquids  and  gases  are  often  poured 
forth  from  volcanoes. 

It  is  hardly  to  be  supposed  that  the  whole  of  the 
earth's  interior  is  a  liquid,  because,  while  the  temper- 
ature may  be  sufficiently  high  to  melt  all  known  sub- 
stances, the  immense  pressure  under  which  all  matter  is 
placed  at  any  great  depth  below  the  surface  must  be 
sufficient  to  retain  it  in  a  solid  form,  notwithstanding 
the  excessive  heat. 
(26) 


LAND  AND   WATER.  27 

As  the  process  of  cooling  went  on,  the  moisture  of  the 
atmosphere  became  condensed  ;  and,  falling  as  rain,  cov- 
ered the  earth's  surface  with  water. 

Out  of  this  primitive  earth,  this  crust  of  mineral  sub- 
stances, and  the  water  and  atmosphere  surrounding  it, 
and  out  of  the  plants  and  bodies  of  animals  that  have 
lived  and  died  upon  its  surface,  have  been  formed  the 
soil  and  rocks  of  our  present  earth. 

The  Age  of  the  Earth.  —  The  processes  by  which  this 
great  change  has  been  brought  about  have  been,  for  the 
most  part,  silent  and  gradual.  Many  of  them  are  still 
going  on.  Our  earth,  with  the  variety  of  substances 
upon  it,  is  not  to  be  considered  as  a  thing  completed,  but 
as  constantly  undergoing  changes  in  the  great  workshop 
of  Nature. 

The  period  of  time  that  has  elapsed  since  the  first 
solid  crust  was  formed  must  be  exceedingly  long.  Some 
of  the  lowest  estimates  made  by  careful  students  have 
been  from  fifteen  to  twenty  million  years. 

Continents.  —  It  is  a  common  principle  in  nature  that 
heating  a  body  causes  it  to  expand,  and  cooling  causes 
it  to  contract,  or  become  smaller.  Now,  it  is  impossible 
for  a  spherical  body,  with  a  solid  surface,  to  become 
smaller  without  forming  upon  its  surface  dents  and 
ridges,  or  depressions  and  elevations.  As  the  ancient 
earth  became  still  cooler  and  smaller,  after  having  first 
formed  a  crust,  it  was  natural  that  this  crust  should  be- 
come irregular  in  shape,  producing  low  and  high  places. 
The  water  naturally  sank  into  the  lower  places,  leav- 
ing the  elevated  regions  as  continents. 

The  continents  that  thus  first  appeared  above  water 
were  very  small,  and  gradually  increased  in  size,  extend- 
ing their  coasts  as  the  continued  shrinking  of  the  crust 


The  Beginnings  of  North  America.    (White  indicates  land.) 


North  America  in  the  Secondary  Era.    (  White  indicates  land.) 
(28) 


LAND   AND  WATER.  29 

raised  them  more  and  more  above  the  level  of  the  water. 
The  first  appearance  of  the  North  American  continent 
was  in  a  small,  angular  section,  extending  from  the  Great 
Lakes  northeast  to  Labrador,  and  northwest  to  the 
Arctic  Ocean. 


North  America  in  the  Tertiary  Era.    (White  indicates  land.) 

Mountains  and  Hills.  — The  cooling  and  shrinking  of  the 
continent  has  also  given  rise  to  mountain  ranges  and 
valleys.  The  imvnnl  pressure  and  sinking  of  certain 
sections  caused  long  cracks  in  the  earth's  crust,  and  the 
upturned  edges  have  formed  some  of  the  great  mountain 
ranges  of  the  earth. 

Some  mountains  have  also  been  formed  by  an  accumu- 
lation of  melted  matter  poured  from  these  cracks  and 
from  volcanoes, 


30  THE  PRINCIPLES  OF  AGRICULTURE. 

Many  of  the  smaller  hills  have  been  formed  by  bodies 
of  moving  water  and  ice,  which  have  ground  out  valleys 
between  them. 

The  formation  of  hills,  and  other  changes  upon  the 
face  of  nature,  have  been  brought  about  gradually.  Fall- 
ing rains  and  running  streams  are  slowly  reducing  the 
size  of  the  hills  by  wearing  them  away  and  carrying  them 
to  the  valleys  below.  In  some  cases,  on  the  other  hand, 
swift  running  streams  and  rivers  are  wearing  out  and 
increasing  the  depth  of  the  valleys  between  the  hills. 

The  Soil  —  If  we  examine  some  soil  with  a  microscope, 
we  shall  find  that,  while  it  contains  some  other  sub- 
stances of  a  different  nature,  a  large  part  of  it  is  com- 
posed of  finely  divided  particles  of  rock.  These  are 
generally  of  a  similar  nature  to  the  larger  rocks  that 
are  scattered  through  the  soil,  and  have  been  produced 
from  large  rocks  by  the  grinding  and  crumbling  forces 
of  nature. 

The  greater  part  of  our  present  soil,  however,  was  not 
formed  directly  out  of  the  original  rocks  of  the  first 
crust  of  the  earth.  The  soil  formed  by  the  first  crumb- 
ling of  the  original  rocks  generally  solidified,  or  petri- 
fied, into  rock  again,  and  this  process  of  crumbling  and 
solidifying  continued  through  several  alternations  until 
our  present  soil  was  formed. 

Nearly  all  the  present  rocks  were  at  some  time  soil. 
Conglomerate  stones,  sometimes  called  "pudding-stones," 
are  examples  of  an  ancient  soil,  containing  stones  of 
different  kinds,  which  has  been  transformed  into  solid 
rock.  Sandstone  was  once  a  bed  of  sand. 

Specimens  of  rocks  from  the  original  crust  are  now  to 
be  found  only  in  a  few  scattered  localities  in  those  sec- 
tions which  first  appeared  above  water,  where,  by  virtue 


LAND   AND 

of  their  elevated  position,  they  have  partly  escaped  the 
forces  that  would  tend  to  destroy  them. 

The  process  of  rock-making  is  still  going  on.  There 
is  often  to  be  found,  beneath  the  surface  soil,  a  stratum 
of  "  hard  pan,"  through  which  it  is  difficult  to  penetrate. 
This  is  gradually  becoming  solidified  by  the  action  of 
chemical  forces,  and  at  some  time  in  the  distant  future 
will  become  stone. 

The  chief  agencies  in  nature  which  have  done  the 
work  of  grinding  rocks,  and  preparing  the  soil  of  the 
earth,  are :  — 

1.  The  Atmosphere.  —  Nearly  all  rocks,  when  exposed  to 
the  atmosphere  above  ground,  undergo  chemical  changes 
upon  their  surface  by  which  portions  are  continually 
crumbling  and  falling  off.     This  effect  upon  some  rocks 
will  cause  them  to  waste  away  in  a  very  few  years,  while 
with  others  the  process  is  much  slower. 

Some  varieties  of  sandstone  are  found  near  the  surface, 
so  much  affected  by  the  atmosphere,  which  has  reached 
them  through  the  porous  soil,  as  to  be  easily  crumbled 
into  powder. 

The  most  enduring  kinds  of  marble,  used  for  erecting 
monuments,  are  generally  covered  with  fine  marble  dust, 
showing  that  even  they  are  not  exempt  from  the  uni- 
versal tendency. 

2.  Running    Water.  --  With  every  shower  and  rain 
storm,  and   with    the    melting    snows    in   spring-time, 
streams  and  brooklets  are  constantly  wearing  away  the 
rocks,  and  washing  away  soil  from  the   sides  of  hills 
and  mountains,  and  carrying  it  into  the  rivers  below. 
As  the  current  of  the  river  becomes  less  rapid,  this  soil 
settles,  forming  deposits  on  the  banks  of  the  river  at  its 
mouth,  or  on  the  neighboring  shores  of  the  ocean. 


32  THE   PRINCIPLES   OF   AGRICULTURE. 

When  the  streams  and  rivers  are  much  swollen,  they 
wash  out  and  bear  away  many  rocks  in  their  swift  cur- 
rent. As  these  are  rolled  and  tumbled  one  upon  an- 
other, they  are  ground  into  soil,  which  is  added  to  the 
general  deposit.  The  mountains  and  hills  are  thus  grad- 
ually carried  away  to  fill  the  valleys  below,  and  to  extend 
the  coasts  of  the  continent.  The  rich  alluvial  lands  in 
river  valleys  have  been  formed  in  this  way. 

3.  The  Ocean.  —  The  movements  of  water  on  the  shores 
of  the  ocean  produce  an  effect  similar  to  that  of  rivers. 
The  flow  and  ebb  of  the  tide,  and  the  breaking  of  waves 
on  the  beach,  grind  rocks  into  sand,  or  wash  tip  shells 
from  deeper  water,  grinding  them  into  (hie  powder.    This 
process  has  been  going  on  since  land  first  appeared  above 
water,  forming  the  origin  of  our  continent. 

The  ocean  has  been  continually  forming  beds  of  sand 
and  mud  on  or  near  its  shores.  These  have  been  raised 
above  the  surface,  as  the  waters  have  receded,  arid  in 
many  cases  have  become  consolidated  into  rock.  Sand- 
stone and  limestone  have  been  mostly  produced  in  this 
manner,  the  former  from  the  sand  beds,  and  the  latter 
from  mud  formed  by  the  grinding  of  shells.  A  similar 
effect  has  been  produced  by  large  lakes,  some  of  which 
have  become  entirely  dry,  leaving  deposits  of  sand,  lime, 
or'  other  mineral  matter. 

4.  Ice.  —  Ice  forming  in  the  cracks  and  crevices  of 
rocks,  year  after  year,  tends  by  its  expansion  to  burst 
the  rocks  or  open  crevices,  thus  admitting  the  atmos- 
phere, and  hastening  the  work  of  crumbling. 

Minute  particles  are  also  detached  from  the  rocks  by 
the  freezing  and  thawing  of  the  moisture  upon  their 
surface.  If  a  number  of  clean  stones  are  placed  in  a 
pail  of  pure  water,  and  the  water  is  allowed  to  freeze 


34  THE  PRINCIPLES  OF  AGRICULTURE. 

and  thaw  several  times,  there  will  be  found  a  perceptible 
quantity  of  fine  particles  at  the  bottom. 

But  the  greatest  effect  of  ice  in  forming  soil,  and 
changing  the  face  of  nature,  has  been  through  glaciers. 

In  high,  mountainous  regions,  and  in  cold  latitudes, 
snow  steadily  accumulates,  forming  immense  masses  of 
ice  in  the  deep  valleys.  These  are  steadily,  but  very 
slowly,  pushed  along  by  their  own  weight  until  they 
reach  a  lower  and  warmer  region,  where  they  melt  away. 
These  huge  rivers  of  moving  snow  and  ice  are  called 
glaciers.  Rocks  in  the  course  of  the  glacier  are  torn  up 
and  borne  along,  grinding  upon  one  another,  and  grind- 
ing paths  through  other  solid  beds  of  rock,  until  they 
are  deposited  as  bowlders  and  soil  at  the  point  where 
the  glacier  melts. 

It  is  believed  that,  at  some  time  in  the  history  of  the 
earth,  the  regions  to  the  north  of  the  equator  became 
for  a  time  much  colder  than  at  present,  causing  perpet- 
ual snow  to  fall  upon  large  portions  of  North  America 
and  Europe,  deep  enough  to  bury  most  of  the  hills  and 
mountains  beneath  vast,  continuous  glaciers. 

These  glaciers,  moving  toward  the  equator,  ground 
enormous  quantities  of  rock  into  soil,  and  deposited  it 
over  a  large  extent  of  country,  together  with  the  rocks 
which  remained  unground.  Huge  bowlders,  as  well  as 
smaller  rocks,  scattered  over  the  country,  may  be  traced 
back  northward  many  miles,  to  their  original  bed.  In 
New  England  they  have  been  carried  two  or  three  hun- 
dred miles,  and  in  the  Mississippi  Valley  one  thousand 
miles.  Soil  and  rocks  which  have  been  transported  in 
this  way  are  called  drift. 

5.  Winds.  —  Winds  have  also  taken  some  part  in  form- 
ing soil,  and  especially  in  changing  its  location.  In 


LAND  AND   WATER.  35 

some  sandy  regions,  large  rocks  have  been  partly  worn 
away  by  the  sand  which  has  for  centuries  been  blown 
across  their  surface.  Whole  hills  have,  in  some  in- 
stances, been  thus  worn  away  and  deposited  in  other 
localities. 

The  Composition  of  Soil.  —  The  soil  of  the  earth  may 
be  considered  as  composed  of  four  different  classes  of 
substances  :  — 

1.  Finely  Divided  Particles  of  Rock.  —  Crumbled  rock, 
or  sand,  constitutes  the  bulk  of  many  varieties  of  soil. 
Even  soft,  peaty  soil  will  be  found,  upon  careful  exam- 
ination, to  contain  a  greater  or  less  percentage  of  gritty 
substance. 

2.  Decaying  Vegetable  Matter.  —  Nearly  all  kinds  of 
soil  contain  more  or  less  of  a  soft,  pasty,  dark-colored 
substance  called  humus,  or  vegetable  mold.    The  grass, 
leaves,  and  falling  trees,  which  are  continually  accumu- 
lating upon  the  surface  of  the  soil,  and  are  mixed  with 
it  by  cultivation,  furnish  a  perpetual  source  of  this  hu- 
mus.    It  forms  a  large  part  of  the  peaty  soil  found  in 
low  places.     In  peat  or  muck  beds  it  is  nearly  pure. 

Peat,  or  swamp  muck,  is  an  accumulation  of  vegetable 
matter  which  has  been  formed  through  long  periods  of 
the  ancient  history  of  the  earth. 

In  low,  marshy  places,  certain  kinds  of  rank  vegeta- 
tion have  grown  year  by  year,  or  from  age  to  age,  and, 
falling,  have  been  buried  one  upon  another  in  water  and 
mud.  These  accumulations  have  undergone  a  process  of 
slow  decay,  or  smothered  combustion,  under  water,  which 
has  reduced  them  to  a  uniform  mass  of  black  or  brown 
matter.  The  dark  color  is  due  to  the  presence  of  carbon 
which  results  from  the  slow  combustion,  as  charcoal  is 
obtained  from  the  smothered  burning  of  wood. 


(36) 


LAND  AND  WATER.  37 

In  some  cases,  in  low  places,  the  process  has  been 
continued  further,  until  the  peat  has  been  petrified,  or 
converted  into  coal. 

Peat  beds  are  very  numerous.  Some  of  them  are  of 
very  large  extent.  The  great  "  Dismal  Swamp  "  of  North 
Carolina  is  a  vast  peat  bed. 

Many  of  the  smaller  muck  swamps  are  partly  com- 
posed of  ordinary  soil,  which  has  been  washed  in  from 
the  surrounding  hillsides. 

3.  The  Remains  of  Animals.  —  The  bones  and  shells 
of  all  the  great  numbers  and  varieties  of  animals  that 
have  lived  and  died   on   the  land,  and   in  the  ocean, 
have  contributed  to  the  formation  of  certain  kinds  of 
soil.     Limestone,  and    limy  matter   in  soil,  have  been 
produced  from  shells  which   have   accumulated  in  the 
ocean,  and  in  lakes  which  have~  become  dry.     The  rock 
of  coral  reefs,  and  the  soil  formed  by  the  crumbling  of 
such  rock,  are  largely  composed  of  the  remains  of  minute 
animals. 

The  bones  of  land  animals,  when  decomposed  or 
ground,  add  desirable  elements  to  the  soil. 

4.  Substances  formed    by    Chemical  Action  from   the 
three  Classes  mentioned.  —  The  presence  of  these  sub- 
stances  gives  fertility  to  the  soil.      Neither  crumbled 
rock,  nor  the  remains  of    plants  or  animals,  in  their 
crude  original   condition,  would    furnish  any  food   for 
the  support  of  plants ;  but  by  chemical  processes  in  the 
soil  new  combinations  are  gradually  formed  which  are 
adapted  to  the  support  of  vegetable  life. 

Soils  are  commonly  classified  according  to  the  sub- 
stances of  which  they  appear  to  be  largely  composed, 
as  follows :  — 

1.    Sandy.  —  Pure  sand,  which  is  composed  entirely 


38  THE  PRINCIPLES  OF  AGRICULTURE. 

of  particles  of  quartz  rock,  would  be  of  little  value  for 
agricultural  purposes.  It  can  furnish  no  food  for  the 
support  of  plants.  It  is  generally,  however,  mixed  with 
other  substances  which  give  it  some  fertility.  Sandy  soil 
has  but  little  power  to  retain  moisture.  Rain  water 
readily  soaks  through  it  and  runs  away.  Such  land  suf- 
fers severely  from  a  drought.  It  is,  furthermore,  unable 
to  retain  for  any  length  of  time  the  supplies  of  plant 
food  which  are  formed  in  it  or  added  to  it.  These  sub- 
stances are  washed  out  as  water  passes  through  it.  It  is 
called  light  soil,  and  has  the  advantage  of  being  easy  to 
till.  It  becomes  dry  and  warm  enough  for  cultivation 
earlier  in  the  spring  than  other  kinds  of  soil. 

2.  G-ravelly.  —  Gravel  is  like  sand,  except  that  the 
rocks  of  which  it  is   composed  have  not  been  ground 
so   fine.     Gravelly  soil   is   largely   composed   of   rocks 
ground  to  various  degrees  of  fineness.     It  has  the  same 
general   properties  as  sandy  soil.     When  nearly  pure, 
it  is  even  less  valuable  than  the  latter  for  agricultural 
purposes. 

3.  Clayey.  —  Clay  consists  of   certain   kinds  of    de- 
composed rock.      Pure  clay,  of  itself,  contains  but  little 
plant  food,  but  it  possesses  in  a  remarkable  degree  the 
property  of   absorbing  and    retaining  other   substances 
which  tend  to  render  it  fertile.     Fertilizers  which  have 
been  applied  to  clayey  soil  are  retained  for  a  long  time, 
until  withdrawn  by  growing  crops. 

Water  leaching  through  such  soil  is  found  to  come 
away  as  pure  as  when  it  enters,  washing  away  no  valu- 
able substances. 

It  is  called  heavy  soil.  Water  passes  through  it  very 
slowly,  so  that  it  cannot  be  tilled  until  late  in  the  spring, 
or  for  a  long  time  after  heavy  rains.  If  handled  and 


LAND  AND  WATER.  89 

pressed  together  when  wet,  it  has  the  peculiar  tendency 
to  form  hard  lumps,  requiring  considerable  labor  to 
pulverize  them  and  provide  a  fine  seed-bed  for  crops. 

4.  Peaty ,  or  Mucky.  —  This  is  one  of  the  most  valu- 
able kinds  of  soil  for  agricultural  purposes.     It  consists 
of  a  mixture  of  ordinary  soil  with  large  quantities  of 
vegetable  mold.     It  has  great  power  to  retain  moisture 
through  periods  of  dry  weather.     It  contains  large  sup- 
plies of  some  kinds  of  plant  food,  which  are  gradually 
converted  into  suitable  form  to  meet  the  demands  of 
successive  crops  year  after  year. 

5.  Limy,   or   Calcareous.  —  Most  soils  contain  some 
lime.    In  some  cases  the  quantity  is  so  large  as  to  give  a 
name  to  the  soil.     The  variety  of  soil  called  marl  con* 
tains  large  quantities  of  carbonate  of  lime. 

The  lime  in  soil  serves  to  some  extent  as  food  for 
plants,  as  all  plants  require  a  small  quantity  of  it.  It 
also  serves  a  good  purpose  indirectly,  as  a  base,  by  com- 
bining with  acid  substances  in  the  soil,  and  forming  salts 
which  are  desirable  as  plant  food. 

6.  Loam.  —  This  is  simply  a  general  name  applied  to 
ordinary  soil,  which  contains  a  mixture  of  the  varieties 
mentioned,   combined   in  varied  proportions.     If   quite 
sandy,  it  is  called  sandy  loam ;  if  quite  clayey,  clayey 
loam. 

QUESTIONS. 

What  was  the  original  condition  of  the  earth  ?  How  did  the  surface 
become  solid  ?  What  is  the  present  condition  of  the  interior  of 
the  earth  ?  How  do  we  know  it  ?  What  caused  the  appearance  of 
water  upon  the  earth  ?  How  old  is  the  earth  ? 

How  were  the  continents  formed?  Explain  the  origin  of  mountain 
ranges  and  hills.  Of  what  is  soil  largely  composed  ?  How  has  it 
been  formed?  Give  the  history  of  most  of  our  present  rocks. 


40  THE  PRINCIPLES  OF  AGRICULTURE. 

Is  any  of  the  first  crust  of  the  earth  still  in  existence  ?  Name  the 
five  natural  agencies  that  have  ground  rocks  into  soil. 

What  is  the  effect  of  the  atmosphere?  What  work  do  streams  and 
rivers  perform  ?  What  has  the  ocean  done  ?  Explain  the  effect 
of  ice  upon  rocks  in  winter.  What  is  a  glacier?  Where  are  gla- 
ciers to  be  found  at  the  present  time?  How  have  glaciers  assisted 
in  forming  soil?  What  has  been  the  effect  of  winds? 

Name  the  classes  of  substances  of  which  soil  is  composed.  Explain 
the  origin  of  humus,  or  vegetable  mold.  Give  the  history  of  the 
formation  of  peat  beds.  What  is  the  origin  of  limestone  ?  Name 
the  different  varieties  of  soil.  Give  the  peculiar  properties  of 
each. 


CHAPTER  III. 

THE  ATMOSPHERE. 

r1HHE   atmosphere   includes   the   air  and  other  gases 
JL       and  vapors  which  surround  the  earth.       Its  com- 
position is  as  follows :  — 

1.  Air.  —  Air  forms  the  bulk  of  the  atmosphere.     It 
is  composed  of  oxygen  and  nitrogen,  in  the  proportion 
of  one  part  oxygen  to  four  parts  nitrogen.     The  two  are 
not  chemically  united  into  molecules,  but  the  molecules 
of  each  are  thoroughly  mixed  together.     It  is  the  oxygen 
of  the  atmosphere  that  is  essential  to  plant  and  animal 
life.     The  purpose  of  the  nitrogen  seems  to  be  to  dilute 
the  oxygen  and  reduce  its  force. 

2.  Water  Vapor.  —  There  is  always  present  in  the  air, 
and  distributed  through  it,  more  or  less  moisture,  or 
vapor  of  water.     The  quantity  varies  from  one  fiftieth  to 
one  two-hundredth  part  of  the  bulk  of  the  air.      This 
moisture  passes    into   the   air  by  evaporation  from  the 
surface  of  bodies  of  water,  from  the  surface  of  the  land, 
and  from  all  moist  substances. 

We  are  reminded  in  various  ways  that  the  air  contains 
moisture,  as  in  the  drops  that  form  upon  the  outside  of  a 
pitcher  of  cold  water,  in  the  moisture  that  accumulates 
upon  the  window-pane  and  forms  a  thick  covering  of  frost 
in  winter  and  in  the  moisture  that  appears  upon  the 
grass  in  the  morning. 

(41) 


42  THE   PRINCIPLES  OF  AGRICULTURE. 

When  the  air  becomes  overcharged  with  moisture,  the 
surplus  comes  to  the  earth  again  in  the  form  of  rain. 

3.  Carbonic  Acid  Gas,  —  The  chief  sources  of  this  gas 
in  the  atmosphere  are  the  breathing  of  animals,  the  burn- 
ing of  fuel,  and  the  decay  of  organic  matter. 

It  is  thrown  off  from  the  systems  of  animals  as  useless, 
but  is  essential  to  the  life  and  growth  of  plants. 

It  may  be  seen  that  the  escaping  breath  contains  car- 
bonic acid,  by  breathing  through  a  tube  into  clear  lime- 
water.  There  will  be  formed  in  the  water  a  white 
powder,  which  is  carbonate  of  lime,  produced  by  the 
union  of  the  carbonic  acid  and  the  lime. 

Although  the  air  always  contains  some  carbonic  acid 
gas,  when  too  large  a  quantity  is  present  it  becomes  poi- 
sonous. For  this  reason  it  is  unwholesome  to  sleep  in 
a  small,  close  room,  without  some  ventilation,  or  for 
many  persons  to  remain  long  in  any  closed  room.  The 
burning  of  lamps  in  a  room,  or  the  decay  of  vegetables 
in  a  cellar,  produces  the  same  effect  as  the  breathing  of 
persons,  by  adding  to  the  proportionate  amount  of  car- 
bonic acid  gas. 

4.  Impurities.  —  The  air  contains  small  quantities  of 
various  substances,  as  ammonia,  nitric  acid,  etc.,  besides 
smoke  and  dust. 

These  are  largely  absorbed  by  the  water  vapor,  and 
brought  to  the  earth  in  raindrops.  They  give  rain-water 
its  dark  color,  and  render  it  of  some  value  as  a  fertilizer 
for  crops. 

Weight  of  the  Atmosphere.  —  The  atmosphere  has  weight 
as  truly  as  the  objects  which  we  can  see  and  handle. 
The  height,  or  distance  from  the  earth  to  which  it  ex- 
tends, is  not  definitely  known.  It  is  variously  estimated 
at  from  one  hundred  to  five  hundred  miles. 


THE  ATMOSPHERE.  43 

It  produces  a  pressure  upon  every  spot  equal  to  the 
weight  of  the  whole  column  above.  This  pressure 
amounts  to  about  fifteen  pounds  upon  every  square 
inch. 

The  pressure  is  not  simply  upon  the  top  of  an  object, 
but  upon  the  sides  and  underneath  as  well.  It  is  not 
like  one  solid  body  resting  upon  another.  The  particles 
of  gases  and  liquids  move  about  so  freely  that  the  pres- 
sure upon  any  object  contained  in  them  is  evenly  distrib- 
uted in  every  direction. 

As  the  pressure  of  the  air  is  evenly  balanced  upon  all 
sides,  we  are  not  conscious  of  it. 

Upon  the  outstretched  hand  there  rests  a  column  of 
air  that  would  weigh  two  or  three  hundred  pounds.  We 
are  not  conscious  of  it,  because  there  is  an  equivalent 
pressure  underneath  the  hand  to  support  it.  When  the 
pressure  underneath  is  removed  by  placing  the  hand 
upon  the  receiver  of  an  air-pump,  and  exhausting  the 
air,  the  pressure  upon  the  top  becomes  painful.  If  the 
moistened  palms  are  rubbed  closely  together,  so  as  par- 
tially to  remove  the  air,  some  force  is  required  to  pull 
them  apart.  If  the  air  is  removed  from  the  mouth  by 
expanding  the  lungs,  the  pressure  of  air  outside  forces 
the  cheeks  inward. 

The  atmosphere  near  the  earth  is  more  compressed 
and  heavy  than  at  some  distance  above  it,  because  there 
is  more  air  above  to  press  down.  There  is  a  marked 
difference  between  the  pressure  and  density  of  air  in 
a  valley  and  on  a  high  mountain. 

The  barometer  is  an  instrument  for  determining  the 
pressure  of  the  air.  It  really  consists  of  a  tube  sealed 
at  one  end,  filled  with  mercury,  and  inverted  into  a  cup 
or  bag  of  mercury.  The  pressure  of  air  upon  the  mer- 


44 


THE  PRINCIPLES  OF  AGRICULTURE. 


cury  in  the  cup  or  bag  forces  this  up  into  the  tube  until 
the  column  of  mercury  in  the  tube  is  heavy  enough  to 
balance  the  pressure  of  the  air.  The  heavier  the  air, 
the  more  it  will  press,  and  the  higher  the  column  will 

rise  in  the  tube.  On  the 
other  hand,  the  lighter  the 
air,  the  lower  the  column 
will  fall. 

Changes  of  temperature 
and  movements  in  the  atmos- 
phere cause  the  weight  and 
pressure  to  vary.  As  this 
variation  is  correctly  deter- 
mined by  the  barometer,  this 
instrument  becomes  of  great 
service  in  calculating  proba- 
ble changes  of  weather. 

Temperature.  —  The  ther- 
mometer is  used  to  deter- 
mine the  temperature,  or  the 
amount  of  heat  that  the  at- 
mosphere contains.  It  con- 
sists of  a  tube,  with  a  bulb 
at  the  lower  end,  containing 
mercury  or  alcohol.  On  the 
principle  that  heat  expands 
and  cold  contracts,  when  the  atmosphere  becomes  warm 
the  mercury  or  alcohol  expands  and  rises  in  the  tubo, 
and  as  the  atmosphere  becomes  cooler  it  contracts  'and 
falls. 

Winds.  —  Since  the  atmosphere  is  invisible,  we  are 
apt  to  forget  that  it  exists,  until  reminded  by  the  force 
of  the  wind  that  it  is  a  real  substance.  Wind  is  simply 


* 


A  Barometer  Tube. 


THE  ATMOSPHERE.  45 

air  in  motion.  Its  force  depends  upon  the  rate  at  which 
the  air  is  moving,  varying  from  a  slight  motion,  which 
gives  a  gentle  breeze,  to  a  velocity  of  forty  or  fifty 
miles  per  hour,  producing  a  hurricane,  a  tornado,  or  a 
whirlwind. 

Cause  of  Winds.  —  Winds  are  always  caused  by  the 
unequal  density  or  weight  of  different  portions  of  the 
atmosphere.  This  is  generally  due  to  differences  in  tem- 
perature. It  is  true  of  the  air,  as  of  other  substances, 
that  heat  expands  it,  making  a  given  bulk  of  it  lighter ; 
and  that  cold  contracts  it,  making  a  given  bulk  heavier. 
If  a  quantity  of  oil  is  poured  into  a  body  of  water,  the 
water,  which  is  heavier,  will  push  the  lighter  oil  to  the 
surface.  So,  if  the  atmosphere  in  any  locality  becomes 
warmer  and  lighter  than  the  surrounding  atmosphere, 
the  latter  will  push  it  into  the  upper  regions,  and  will 
rush  in  to  fill  the  space  underneath. 

The  high  wind  that  accompanies  a  thunder-storm  at 
the  close  of  a  hot  day  is  due  to  the  fact  that  the  atmos- 
phere, which  has  been  heated  during  the  day,  is  now 
rapidly  rising,  while  the  cooler  atmosphere  around  is 
rushing  in. 

The  land  and  sea  breezes,  which  are  common  on  the 
sea-coast,  are  due  to  the  unequal  heating  of  the  atmos- 
phere over  land  and  water  at  different  times  of  day. 

Rain.  —  Rain  is  an  accumulation  of  the  vapor  of  the 
atmosphere  into  drops,  which,  by  their  weight,  fall  to  the 
ground.  There  is  a  limit  to  the  quantity  of  water  which 
the  air  is  capable  of  absorbing  and  retaining  as  an  invis- 
ible vapor.  When  it  contains  as  much  as  possible,  it  is 
said  to  be  saturated.  Now,  warm  air  is  able  to  hold  more 
moisture  than  cold  air  ;  hence,  when  air  which  is  satu- 
rated becomes  colder,  for  any  reason,  it  can  no  longer 


46  THE  PRINCIPLES  OF  AGRICULTURE. 

retain  all  its  moisture.  A  portion  is  liberated,  accu- 
mulates in  drops,  and  falls  to  the  earth.  This  is  in 
all  cases  the  explanation  of  rain. 

The  different  ways  in  which  the  air  is  cooled,  and  rain 
is  produced,  are :  — 

1.  By  Rising  into  the  Upper  Regions.  —  The  higher  we 
ascend  from  the  earth's  surface,  the  cooler  we  find  the 
atmosphere.       Mountains   are   sometimes   clothed  with 
grass  and  flowers  at  the  foot,  while  their  summits  are 
covered  with  perpetual  snow. 

The  atmosphere  is  warmed  chiefly  by  the  warm  earth. 
The  heat  of  the  sun's  rays  is  accumulated  upon  the 
surface  of  the  earth.  The  earth  then,  like  a  heated 
stove,  throws  out  or  radiates  its  heat,  and  warms  the 
atmosphere.  So,  as  in  case  of  the  stove,  the  atmosphere 
nearest  it  is  always  the  warmest. 

As  the  air  in  any  locality  becomes  heated  in  this 
way,  it  is  pressed  upward  by  cooler  and  heavier  air  from 
other  sections,  where  it  is  cooled;  and,  if  it  contains 
sufficient  moisture,  rain  is  produced. 

Ascending  air  is  also  cooled  by  expanding.  When  air 
is  compressed  so  as  to  occupy  a  smaller  space,  it  becomes 
warmer.  On  the  other  hand,  when  air  expands,  it  be- 
comes cooler.  As  the  air  ascends,  the  pressure  upon  it 
from  the  air  above  becomes  less,  and  consequently  it 
expands  and  becomes  cooler.  This,  of  itself,  is  a  com- 
mon cause  of  rain. 

2.  By  Passing  over  Mountains.  —  Hills  and  mountains 
are  sometimes  called  "  rain  condensers."     As  the  rising 
currents  of  air  pass  over  mountainous  regions,  the  air  ex- 
pands and  is  cooled,  and  parts  with  its  surplus  moisture. 
Hilly  regions  are  more  abundantly  supplied  with  rain 
than  level  tracts.     That  side  of  a  range  of  mountains 


THE  ATMOSPHERE. 

which  the  wind  reaches  first  in  its  customary  course 
receives  more  rain  than  the  opposite  side,  since  the  cur- 
rents of  air  lose  moisture  in  passing  over  it.  The  absence 
of  rain  on  some  parts  of  the  coast  of  South  America  is 
due  to  the  fact  that  the  wind,  which  blows  constantly 
from  the  east  in  those  regions,  causes  the  atmosphere  to 
deposit  rain,  and  become  comparatively  dry  in  passing 
the  Andes  Mountains. 

3.  By  the  Mixture  of  Warm  and  Cool  Currents  of 
Air.  —  In  the  changing  courses  of  variable  winds,  warm 
currents  of  air  often  meet  and  mingle  with  cooler  cur- 
rents. When  the  air  is  saturated,  this  is  liable  at  any 
time  to  cause  rain. 

Snow  and  Hail,  —  Snow  and  hail  are  frozen  forms  of 
atmospheric  moisture.  In  the  case  of  snow,  the  minute 
particles  of  moisture  are  frozen  as  they  form,  and  arrange 
themselves  about  each  other  in  beautiful  crystals,  pro- 
ducing the  snowflake. 

Hailstones  are  often  formed  by  whirling  currents  of 
wind,  which  carry  raindrops  or  minute  snowballs  first 
into  the  upper,  cold  regions,  where  they  are  frozen, 
then  downward  through  a  warmer  section,  where  more 
water  is  added,  and  then  upward  again.  The  size  of  the 
stones  is  thus  gradually  increased  until  they  become  too 
heavy  to  be  carried  upward  again,  and  are  flung  to  the 
earth. 

Fogs,  Mists,  and  Clouds.  —  These  are  all  of  the  same 
nature.  They  are  simply  particles  of  water  or  ice  which 
have  formed  at  points  where  currents  of  air  of  different 
temperatures  meet  each  other,  but  not  in  sufficient  quan- 
tity to  produce  raindrops. 

Clouds  are  formed  wherever  the  air,  in  rising,  is  cooled 
enough  to  condense  vapors.  When  the  air  is  quite  dry, 


48  THE   PRINCIPLES  OF   AGRICULTURE. 

clouds  will  not  be  formed  until  a  high  point  is  reached, 
if  at  all.  When  it  is  well  saturated,  they  may  be  formed 
so  low  as  to  touch  the  earth,  and  are  then  called  fogs  or 
mists. 

Dew.  —  Dew,  like  rain,  fog,  etc.,  is  caused  by  the  cool- 
ing of  the  atmosphere.  The  earth  during  the  night  be- 
comes cooler  than  the  air  above  it,  and  tends  to  condense 
moisture  from  the  air  which  comes  in  contact  with  it. 

There  is  less  dew  on  a  cloudy  night,  because  clouds 
prevent  the  earth  from  cooling.  They  obstruct  the  rays 
of  heat  a.s  these  pass  from  the  earth,  and  turn  them 
back,  thus  preserving  an  equality  of  temperature  be- 
tween the  earth  and  the  air. 

A  strong  wind  prevents  the  formation  of  dew  by  keep- 
ing the  air  well  mixed,  and  leaving  no  part  of  it  in  con- 
tact with  the  ground  long  enough  to  become  cool  and 
deposit  moisture. 

A  slight  breeze  increases  the  amount  of  dew  by 
removing  those  portions  of  air  which  have  already 
deposited  their  moisture,  and  bringing  other  portions 
successively  in  contact  with  the  ground. 

The  quantity  of  water  that  forms  upon  the  ground  as 
dew  is  much  larger  than  is  generally  supposed.  It  is 
only  a  portion  of  it  that  appears  in  the  morning  on  the 
blades  of  grass.  A  large  part  is  absorbed  into  the  soil. 

In  Great  Britain,  where  dews  are  heavy,  it  is  esti- 
mated that  the  whole  amount  deposited  in  a  year  would 
be  equal  to  a  depth  of  several  inches  of  water.  In  some 
tropical  regions  it  is  deposited  so  fast  as  to  be  equal  to  a 
light  rain. 

Frost  —  Frost  is  simply  frozen  moisture  from  the  at- 
mosphere. When  the  temperature  at  the  point  where 
dew  would  form  falls  below  32°,  the  point  at  which  water 


THE  ATMOSPHERE. 


49 


freezes,  the  moisture  condensed  from  the  air,  instead  of 
forming  dew,  forms  crystals  of  ice,  or  frost. 

When  there  is  110  dew,  there  can  be  no  frost  of  this 
kind,  and  vegetation  is  not  injured  unless  the  temper- 
ature falls  low  enough,  and  remains  low  long  enough  to 
freeze  the  sap  within  the  plant. 


^ ^  Isobars,  every  fifths  of  an  inch  difference Direction  of  wind  &  clear  weather 

of  pressure.  <t         i<     u     tt    ,      ,       u 

•  Isotherm*,  errri/  10  dcyrees  temperature.   ~ °~+ 

"  Low  "  =  Center  of  (' i/clone.  — •—  '    ''"'"• 

"///</A"--  Aiiticii<l<»ies.  m_         <«          "      "      "snow. 

^» V-  path   of  Cyclone. 

Weather  Map. 

The  Weather.  —  The  changes  of  weather  which  are  con- 
stantly taking  place  are  not.  irregular  and  accidental. 
They  occur  according  to  certain  laws,  and  as  the  result 
of  certain  causes.  By  ascertaining  these  causes,  it  is 
possible  to  predict  changes,  so  that  a  storm,  or  a  cold  or 
warm  wave  of  temperature,  may  be  foretold  some  hours 
before  it  appears. 
WINS.  Ao.  —  4. 


50  THE  PRINCIPLES  OF  AGRICULTURE. 

The  provision  made  by  the  United  States  for  noting 
conditions,  and  announcing  indications,  in  all  parts  of 
the  country,  is  of  great  importance.  It  is  of  great  value 
in  agriculture.  The  farmer,  relying  upon  these  indica- 
tions, may  select  favorable  weather  for  planting  his  seed 
or  harvesting  his  crops. 

Storms,  —  The  central  section  of  a  storm  is  noted  by 
an  area  of  low  barometer,  or  low  pressure.  That  is 
to  say,  it  is  where  the  atmosphere  is  lighter  than 
usual,  and  on  that  account  is  rising.  In  front  and  in 
the  rear  of  the  storm  center,  the  barometer  is  high,  or 
the  atmosphere  is  heavy.  In  the  United  States,  these 
sections  of  low  pressure,  which  mark  the  location  of 
storms,  are  generally  long  and  narrow,  extending 
across  the  country  from  north  to  south.  Storms  usu- 
ally appear  first  in  the  western  or  southern  parts  of 
the  country,  and  move  in  an  easterly  or  northeasterly 
direction. 

Naturally,  the  winds  on  both  sides  of  the  storm  center 
blow  toward  it.  They  are  the  heavier  sections  of  air 
passing  in  to  take  the  place  of  the  lighter  sections,  which 
are  rising ;  hence,  storms  are  generally  preceded  by  east, 
northeast,  or  southeast  winds,  and  followed  by  west, 
northwest,  or  southwest  winds. 

Climate.  —  The  climate  of  a  region  is  its  condition  with 
regard  to  heat  and  moisture.  It  may  be  considered  a  hot 
or  cold,  a  moist  or  dry  climate. 

The  temperature  in  any  locality  depends  chiefly  upon 
the  following  conditions  :  — 

1.  Latitude.  —  The  extent  to  which  the  earth  and  the 
atmosphere  near  it  become  heated  depends  upon  the  di- 
rectness with  which  the  rays  of  heat  from  the  sun  fall 
upon  it.  Sections  near  the  poles  are  therefore  colder 


THE  ATMOSPHERE.  51 

than  those  near  the  equator,  which  have  the  sun  more 
directly  overhead. 

2.  Elevation.  —  As  the  atmosphere  is  cooler  the  higher 
we  ascend,  so  the  climate  of  elevajbed  tracts  is  colder  than 
that  of  low  plains  and  valleys.     Although  the  high  re- 
gions receive  the  full  benefit  of  the  sun's  heat,  they  lose 
heat  rapidly,  since  the  atmosphere  in  these  regions,  be- 
ing thin  and  dry,  permits  the  heat  to  pass  off  easily  by 
radiation. 

3.  Nearness  to  the  Ocean.  —  The  tendency  of  the  ocean 
is  to  render  the  climate  uniform,  —  cooler  in  summer 
and  milder  in  winter.     As  the  water  upon  the  surface  of 
the  ocean  becomes  heated  by  the  sun,  it  mingles  with 
the  cooler  water  below.     This  prevents  the  surface  water 
from  becoming  very  warm,  and  from  imparting  heat  rap- 
idly to  the  atmosphere. 

As  the  ocean  has  stored  a  large  amount  of  heat,  and 
has  become  heated  to  a  considerable  depth,  it  is  not 
quickly  cooled  as  winter  approaches,  but  parts  with  its 
warmth  gradually  during  the  entire  winter. 

The  solid  land,  on  the  other  hand,  does  not  become 
heated  to  a  great  depth.  The  heat  of  the  sun  is  concen- 
trated upon  its  surface,  and  is  more  readily  radiated  into 
the  atmosphere. 

In  the  fall  of  the  year  the  ground  is  more  quickly 
cooled,  and  has  less  influence  in  tempering  the  severity 
of  winter. 

Near  the  coast,  the  climate  is  rendered  comparatively 
uniform  by  receiving  the  benefit  of  cool  winds  from  the 
sea  in  summer  and  mild  winds  in  winter. 

The  amount  of  moisture  depends  mostly  upon  the 
nature  of  the  surroundings  and  the  direction  of  prevalent 
winds. 


52  THE  PRINCIPLES  OF  AGRICULTURE. 

Hilly  and  mountainous  regions,  which  the  winds  reach 
first  in  their  usual  course,  are  generally  well  supplied, 
while  more  level  regions  farther  on  have  a  drier  climate. 


QUESTIONS. 

Of  what  is  the  atmosphere  composed  ?  What  are  the  two  elements  of 
air  ?  Which  of  them  is  the  more  important  V  Of  what  use  is  nitro- 
gen in  the  air  ?  How  much  water  vapor  does  the  air  contain  ?  Where 
does  the  air  get  it  ?  What  becomes  of  it  when  there  is  more  than  the 
air  can  hold  ?  In  what  three  ways  is  the  carbonic  acid  gas  of  the 
atmosphere  formed  ?  Name  some  of  the  impurities  found  in  the 
atmosphere.  What  finally  becomes  of  these? 

How  much  does  the  atmosphere  weigh  ?  Why  is  its  pressure  greater 
in  a  valley  than  on  a  mountain?  Is  the  atmosphere  heavier  or 
lighter  in  stormy  weather  ? 

What  is  a  barometer  ?  Why  does  the  barometer  fall  before  a  storm  ? 
In  which  direction  does  the  atmosphere  press  ?  How  many  pounds 
of  air  rest  upon  your  outstretched  hand  ?  How  are  you  able  to  lift 
so  great  a  weight  ? 

What  is  a  thermometer  ?  What  causes  the  mercury  to  rise  and  fall 
in  a  thermometer  ? 

What  is  the  wind?  What  causes  the  wind  to  blow?  Describe  the 
direction  of  the  currents  of  air  in  a  room  with  a  hot  stove  at  one 
side.  What  causes  a  sea  breeze  in  a  hot  day  on  the  coast  ?  Why 
is  a  thunder-shower  usually  accompanied  by  wind  ? 

What  is  rain  ?  In  what  three  ways  is  rain  produced  ?  Why  is  the 
air  always  warmer  near  the  earth  than  away  from  it  ?  Why  are 
hills  and  mountains  cooler  than  low  places  ?  Why  is  there  gener- 
ally an  abundance  of  rain  on  that  side  of  a  mountain  range  from 
which  the  wind  blows  ? 

What  is  snow?  Explain  the  formation  of  hailstones.  Why  does  it 
sometimes  hail  when  the  temperature  is  below  the  freezing  point? 
How  can  it  snow  when  the  temperature  is  above  freezing? 

What  are  fogs,  mists,  and  clouds  ?  What  determines  the  height  of 
clouds?  Why  is  it  always  cloudy  before  it  rains  ? 

Explain  the  cause  of  dew.  How  do  clouds  prevent  the  formation  of 
dew  ?  Why  is  there  no  dew  upon  a  windy  night  ?  What  is  the 


THE  ATMOSPHERE. 


effect  of  a  slight  breeze  ?  Give  some  idea  of  the  quantity  of  dew. 
What  causes  drops  of  water  to  form  upon  a  pitcher  of  cold  water 
on  a  hot  day  ? 

What  is  frost  ?  When  is  frost  liable  to  occur,  and  when  not  ?  Upon 
which  side  of  a  window  does  frost  form  ?  Why  is  there  less  frost 
on  the  windows  of  a  vacant  room  than  on  those  of  a  room  full  of 
people  ? 

Are  the  changes  of  weather  accidental  ?  What  is  the  work  of  the 
Weather  Bureau,  established  by  the  government?  Of  what  ad- 
vantage is  it  to  the  farmer?  What  is  the  general  cause  of  a 
storm  ?  Describe  the  general  course  of  storms  in  the  United  States. 
Which  way  do  the  winds  naturally  blow  at  the  time  of  a  storm, 
and  why? 

What  is  meant  by  climate  ?  What  three  general  conditions  deter- 
mine the  temperature  of  a  locality  ?  Why  is  the  temperature  over 
the  ocean  more  uniform  than  over  the  land  ?  Why  are  winters 
usually  most  severe  in  the  center  of  a  continent  ?  What  generally 
determines  the  amount  of  rain  in  any  locality  ? 


CHAPTER  IV. 


PLANTS. 

Seeds.  —  The  growth  of  a  plant  begins  with  the  seed. 
A  seed  contains  all  the  essential  parts  of  the  plant  it- 
self, ready  to  be  extended  outward  into  the  soil  and  into 
the  atmosphere  as  soon  as  favorable  conditions  are  sup- 
plied. This  minute  plant  found  in  the  seed  is  called  the 
"embryo,"  or  "germ." 

Besides  the  germ,  a  seed  contains  a  quantity  of  food, 
stored  up  to  supply  the  young  plant  as  it  begins  to  grow, 

until  it  is  able  to  pro- 
vide for  itself  from 
the  soil  and  the  at- 
mosphere. 

In  the  "chit"  of  a 
kernel  of  corn,  and  at 
the  "  eye  "  of  a  bean, 
the  embryo  is  to  be 
found.  The  remainder  of  the  seed  is  composed  of 
starch  and  other  substances  for  the  young  plant  to 
feed  upon. 

The  Vitality  of  Seeds.  —  Different  varieties  of  seeds  dif- 
fer greatly  in  the  length  of  time  they  maintain  their 
vitality,  or  power  to  sprout  and  produce  growth.  The 
seeds  of  some  trees  will  not  sprout  at  all  after  once  be- 
coming dry.  On  the  other  hand,  some  seeds,  if  kept 
dry,  will  grow  after  many  years.  When  sealed  away 
from  the  air,  these  seem  to  retain  their  vitality  almost 
(64) 


Sections  of  a  Grain  of  Corn,  and  the  Germ 
detached. 


55 

indefinitely.  Peas  are  said  to  have  sprouted  which 
were  taken  from  an  Egyptian  mummy  three  thousand 
years  old. 

It  is  better  to  select  new  seeds  for  planting.  Older 
seeds  may  grow,  but  will  generally  produce  weaker 
plants. 

Unripe  Seeds.  —  Seeds  used  for  planting  should  always 
be  thoroughly  ripe.  The  loss  from  planting  unripe  corn, 
or  "  pinched  "  wheat,  may  be  many  times  as  great  as  the 
extra  cost  of  better  seeds. 

While  the  difference  in  yield  resulting  from  poor  seeds 
may  not  always  be  apparent  the  first  season,  if  the  prac- 
tice is  continued  through  a  number  of  years  the  crop 
will  "  run  out "  and  become  unprofitable. 

On  the  other  hand,  by  selecting  the  best  specimens  of 
seeds,  year  after  year,  the  crop  will  be  greatly  improved. 
The  yield  of  different  crops  has,  in  some  instances,  been 
doubled  by  a  continuous  selection  of  the  best  seeds. 

Conditions  of  Growth.  —  There  are  three  conditions  re- 
quired for  the  growth  of  seeds,  all  of  which  must  be  sup- 
plied in  order  to  produce  germination. 

1.  Moisture.  —  When  a  dry  seed  is  placed  in  soil,  or 
some  other  moist  substance,  it  immediately  begins  to 
absorb  moisture;  it  swells,  and  if  the  temperature  is 
favorable  and  sufficient  air  is  supplied,  it  puts  forth  its 
root,  and  begins  to  grow. 

The  amount  of  moisture  favorable  for  growth  varies 
with  different  seeds.  Some  varieties  will  grow  in  water, 
some  thrive  best  in  very  moist  soil,  while  others  require 
comparatively  dry  soil. 

It  is  believed  that  some  varieties  of  seeds  are  covered 
with  a  coating  through  which  water  cannot  penetrate, 
and  that  these  may  remain  in  the  soil  for  an  indefinite 


56  THE  PRINCIPLES  OF  AGRICULTURE". 

period  without  germinating,  until  the  hull  is  accidentally 
scratched,  or  broken,  so  as  to  admit  moisture.  This  may 
account  for  the  fact  that  so  many  weeds  unexpectedly 
and  repeatedly  spring  up  after  the  soil  is  stirred  in  cul- 
tivating crops. 

2.  Warmth.  —  There  is  a  certain  range  of  temperature 
within  which  a  seed  will  grow,  and  outside  of  which  it 
will  fail  to  do  so. 

The  seeds  of  some  plants,  whose  native  home  is  in  cold 
climates,  will  sprout  at  a  low  temperature,  while  others, 
which  are  accustomed  to  a  warmer  climate,  require  a 
higher  temperature.  The  lowest  point  of  temperature  at 
which  wheat,  barley,  oats,  and  peas  will  sprout  is  about 
40°,  and  the  highest  about  103°.  The  lowest  for  corn 
and  squashes  is  about  50°,  and  the  highest  about  115°. 

Although  the  seeds  may  sprout  at  any  point  within 
this  range  of  temperature,  at  a  point  near  either  extreme 
growth  will  be  very  slow,  and  the  plants  weak  and  small. 
There  is  a  certain  degree  of  heat  for  each  variety  of 
seeds  in  which  they  will  produce  the  best  growth.  That 
point  for  wheat,  oats,  and  barley  is  about  84°,  and  for 
corn  and  squashes  about  94°.  The  nearer  we  approach 
to  this  favorable  point  in  choosing  the  land  and  the 
time  for  planting,  the  better  the  results.  The  mistake 
is  often  made  of  planting  seeds  too  early  in  the  spring, 
before  the  ground  is  sufficiently  warm  to  insure  quick 
and  strong  growth.  '  The  early  plant  is  so  weakened 
by  low  temperature  as  to  gain  nothing  in  the  end  over 
the  later  plant,  which  thrives  better,  and  yields  larger 
results. 

3.  Oxygen. — Oxygen,  which  is  essential   to  support 
life  in  animals,  being  taken  into  their  systems  through 
the  air   in  their  lungs,  is  also  essential  to  the  life  and 


FLANTS.  5? 

growth  of  plants,  and  even  to  the  sprouting  of  seeds. 
Soil  is  always  more  or  less  porous  near  its  surface,  and 
it  is  filled  with  air,  which  supplies  the  sprouting  seed 
with  oxygen. 

Depth  of  Planting,  —  Most  seeds  would  sprout  and  grow 
if  dropped  upon  the  surface  of  the  soil  in  a  rainy  season, 
when  the  atmosphere  is  damp  enough  to  supply  the 
needed  moisture,  but  it  is  generally  safer  and  better  to 
cover  them  with  soil. 

The  proper  depth  of  planting  will  depend  upon  the 
nature  of  the  soil,  climate,  crop,  etc.  In  very  wet  or 
cold  seasons,  it  is  better  to  cover  the  seed  but  little,  so 
that  it  may  have  better  access  to  the  air  and  the  warmth 
of  the  sun.  In  warm,  dry  seasons,  it  should  be  buried 
more  deeply,  so  as  to  secure  sufficient  moisture. 

In  some  sections  of  the  country,  and  in  some  special 
seasons,  Indian  corn  will  thrive  best  when  planted  at  a 
depth  of  several  inches,  while  ordinarily  a  light  covering 
is  better. 

Many  kinds  of  seeds  will  not  grow  at  all  if  buried 
deeply.  The  seeds  of  weeds  remain  dormant  in  the  soil, 
until  they  are  brought  near  the  surface  by  plowing  or 
harrowing,  where  sufficient  air  and  heat  are  supplied, 
and  then  they  spring  up  and  grow  vigorously. 

Seeds  are  supposed  to  contain  a  supply  of  nourishment 
sufficient  to  support  the  young  plant  until  the  ascending 
stem  can  reach  the  open  air. 

In  some  cases  of  deep  planting,  while  there  may  be 
oxygen  enough  to  produce  growth,  the  supply  of  food  in 
the  seed  becomes  exhausted  before  the  surface  is  reached, 
and  the  plant  perishes. 

Germination.  —  The  process  of  germination,  or  sprout- 
ing of  seeds,  includes  three  points. 


58  THE  PRINCIPLES  OF  AGRICULTURE. 

1.  The  Absorption  of  Moisture.  —  It  is  evident  that 
the  nutritive  substances  contained  in  the  seed  cannot 
pass  into  the  plant  and  support  growth  while  in  a  dry 
state.   The  seed  must  be  saturated  with  moisture,  so  that 
there  may  be  a  medium  through  which  these  substances 
may  pass  to  the  point  in  the  growing  plant  where  they 
are  needed. 

2.  A  Change  in  the  Nutritive  Substances.  —  The  sup- 
plies of  food  stored  in  the  seed  are  not  generally  in  a 
suitable  form  to  support  the  plant,  but  must  first  be 
changed.     They  are  dissolved  in  the  moisture,  and  con- 
verted by  chemical  processes  into  the  proper  forms.    An 
instance  of  this  is  the  conversion  of  starch  into  sugar. 
The  formula  for  starch  is  C6Hi005,  and  for  the  glucose 
sugar  obtained  from  it,  C6Hi206.     The  latter  is  obtained 
from  the  former  by  the  addition  of  oxygen  and  hydrogen. 

In  the  process  of  malting  barley  and  other  kinds  of 
grain,  the  aim  is  to  obtain  these  same  chemical  changes. 
The  grain  is  soaked  and  allowed  to  sprout  until  the 
starch  and  other  substances  are  converted  into  sugar, 
dextrine,  etc.  The  process  is  then  stopped  by  drying, 
and  the  new  substances  are  extracted  from  the  grain  to 
form  malt. 

3.  The  Production  of  Heat.  —  The  changes  above  re- 
ferred to  are  largely  due  to  oxidation,  or  the  combina- 
tion of  oxygen  with  the  substances  of  the  seed.     This, 
as  in  other  instances  of  oxidation,  produces  heat. 

If  a  large  number  of  seeds  are  heaped  together,  as  in 
manufacturing  malt,  the  mass  becomes  very  warm,  —  so 
much  so  that  care  is  required  to  prevent  the  grain  from 
spoiling.  This  heat,  developed  in  the  sprouting  seed,  is 
of  some  service  at  times  when  the  temperature  outside 
is  too  low. 


PLANTS. 


59 


Growth  from  the  Seed.  —  From  the  seed  first  appears  a 
shoot,  called  the  radicle,  which  extends  downward  into 
the  soil,  and  shortly  afterward  another  shoot,  called  the 
plumule,  which  seeks  to  find  its  way  upward  into  the  air 
and  sunlight.  The  radicle  is  the  origin  of 
the  roots  of  the  plant,  and  the  plumule  the 
origin  of  the  stem,  with  its  branches  and 
leaves. 

The    reason   why   the    root    thus   turns 
downward  and  the  stem  upward  is  an  un- 
solved mystery.     It  cannot  be  due  to  any 
attractive  force  of  light  upon  the  stem,  or 
any  repelling  force  upon  the  root,  as  it  has 
been  found  that  the  same   directions   are 
followed  when  a  seed  is  sprouted  in  the  air, 
in  absolute  darkness.     From  this  and  from 
other  habits  of  plants,  it  would  seem  that 
they  are  endowed  with  a  kind  of  instinct, 
similar  to  the  instincts  of  animals.     Some 
plants  always  turn  their  leaves  toward  the 
sunlight,  while   others   turn   them   away.   Germination  of 
Some  flowers  close  in  the  afternoon  and 
open  in  the  early  morning.     These  facts    ^aLL'fthe' coty. 
we  cannot  account  for  with  certainty,  in    lr€dr°^^lumulei 
a  scientific  way,  any  more  than  we  can  ac- 
count for  the  very  principle  of  life  which  causes  the  seed 
to  begin  to  germinate  and  its  growth  to  continue. 

Two  Worlds  for  the  Plant.  —  A  plant  has  two  worlds, 
or  feeding  grounds :  the  atmosphere  above  and  the  soil 
beneath.  One  is  as  essential  to  the  life  and  welfare  of 
the  plant  as  the  other.  As  plants  cannot  live  when  their 
roots  are  withdrawn  from  the  soil,  so  also  most  plants 
will  die  if  the  portion  above  the  surface  is  repeatedly  cut 


60  THE  PRINCIPLES  OF  AGRICULTURE. 

off.     Out  of  the  soil  and  the  atmosphere  they  obtain  the 
food  which  sustains  their  life  and  growth. 

The  Food  of  Plants,  —  If  we  analyze  the  substances  of 
which  a  plant  is  composed,  and  ascertain  the  elements 
which 'it  contains,  we  shall  know  exactly  what  food  it  re- 
quires, and  what  the  soil  and  atmosphere  must  contain 
in  order  to  afford  proper  nourishment. 

The  following  elements  are  found  in  all  plants,  and 
are  essential  to  their  growth :  carbon,  hydrogen,  oxy- 
gen, nitrogen,  sulphur,  phosphorus,  potassium,  calcium, 
magnesium,  and  iron.  Besides  these,  there  are  generally 

found  sodium,  silicon, 
chlorine,  and  traces 
of  some  other  sub- 
stances. 

Food  from  the  At- 
mosphere.—  The  food 
Avhich  plants  obtain 
from  the  atmosphere 
is  mostly  carbon.  The 
leaves  absorb  carbonic 
acid  gas  (C02),  and 
separate  the  carbon 
from  the  oxygen,  re- 
The  under  side  of  a  Leaf .  taining  the  former 

(Magnified,  showing  Cells  and  Mouths,  or  Stoinata.)          n 

and  returning  the  lat- 
ter to  the  atmosphere.  This  carbon,  combining  with 
hydrogen  and  oxygen  in  the  plant,  is  converted  into 
starch,  sugar,  cellulose,  etc.,  and  thus  enters  into  the 
structure  of  the  plant. 

This  process  of  absorbing  and  decomposing  carbonic 
acid  gas  takes  place  only  in  sunlight.  In  some  unknown 
way,  the  influence  of  the  rays  of  light  is  required  to 


PLANTS.  61 

effect  the  change.  For  this  reason  a  continuation  of 
dark,  rainy  weather  is  injurious  to  the  growth  of  most 
plants.  In  such  weather  they  turn  pale  from  the  absence 
of  coloring  material,  which  requires  the  aid  of  sunlight 
for  its  formation. 

The  air  is  admitted  to  the  interior  of  a  leaf  through 
minute  openings,  or  mouths,  which  generally  exist  in 
great  numbers.  Upon  an  ordinary  apple  leaf  there  may 
be  found  as  many  as  100,000  of  these  openings. 

Plants  Purify  the  Air.  —  This  absorption  of  carbonic 
acid  and  liberation  of  oxygen  are  of  the  greatest  impor- 
tance to  animal  life. 

In  the  lungs  of  men  and  other  animals,  oxygen  from 
the  air  is  continually  absorbed  into  the  blood,  and  in 
place  of  it  carbonic  acid  gas  passes  from  the  lungs  with 
the  breath.  An  accumulation  of  this  gas  in  the  atmos- 
phere would  soon  become  poisonous,  but  the  danger  is 
avoided,  and  the  balance  maintained,  by  the  fact  that  all 
growing  vegetation  is  constantly  withdrawing  carbon  and 
setting  oxygen  free.  It  is  estimated  that  an  acre  of 
forest  trees  will  consume  the  carbonic  acid  produced 
by  the  breathing  of  fifteen  men. 

In  this  way  vegetable  and  animal  life  mutually  benefit 
each  other,  each  requiring  and  making  use  of  that  ele- 
ment which  is  rejected  by  the  other. 

Do  Plants  Breathe  "?  —  While  plants  are  taking  in  car- 
bon and  throwing  out  oxygen,  they  are  at  the  same  time, 
1  hough  only  to  n  slight  extent,  doing  exactly  the  reverse, — 
inking  in  oxygen  and  throwing  out  carbonic  acid.  This 
is  very  similar  to  the  act  of  breathing  in  animals. 

It  would  seem  unnecessary  for  the  plant  to  take  these 
two  seemingly  opposite  courses,  but  they  are  for  entirely 
different  purposes. 


62  THE  PRINCIPLES  OF   AGRICULTURE. 

The  process  of  breaking  up  the  molecules  of  carbonic 
acid,  and  retaining  the  carbon,  requires  the  aid  of  sun- 
light, and  is  really  a  process  of  feeding,  or  upbuilding  the 
plant ;  but  the  act  of  breathing,  or  taking  oxygen  from 
the  air,  goes  on  continuously  through  the  night,  and  is  a 
process  of  oxidation  or  slow  burning  and  destruction  of 
the  plant. 

Absorption  of  Water. — But  little  water,  if  any,  is  ab- 
sorbed by  leaves  from  the  atmosphere.  A  drooping  plant 
is  quickly  revived  by  watering,  or  by  a  shower  of  rain, 
not  so  much  by  absorbing  moisture  through  its  leaves  as 
by  the  rapid  passage  of  water  into  the  stem  and  leaves 
through  its  roots. 

Nitrogen  from  the  Air.  —  While  free  nitrogen  constitutes 
four  fifths  of  all  the  air,  it  has  generally  been  believed 
that  none  of  this  is  directly  available  for  the  use  of 
plants.  Recent  investigations,  however,  show  that  cer- 
tain varieties  of  plants  are  probably  able,  in  some  way, 
to  make  direct  use  of  atmospheric  nitrogen.  This  seems 
to  be  especially  true  of  the  family  of  plants  called  legumi- 
nous, or  pod-bearing  plants.  This  family  includes  peas, 
beans,  clover,  lucern,  etc. 

Ammonia,  which  exists  in  small  quantities  in  the 
atmosphere,  is  partly  composed  of  nitrogen,  and  it  is 
thought  the  plant  may  obtain  a  little  nitrogen  by  ab- 
sorbing this  gas  through  its  foliage. 

Roots.  —  The  purpose  of  the  root  is  to  give  the  plant 
support,  holding  it  firmly  in  position ;  to  absorb  nourish- 
ment  from  the  soil;  and,  in  the  case  of  biennial  plants, 
to  store  up  a  supply  of  food  to  support  the  plant  the 
second  year. 

The  radicle,  or  first  root  which  descends  into  the  soil 
from  the  seed,  soon  subdivides  into  a  number  of  small 


PLANTS. 


63 


roots  which  extend  in  different  directions,  or  sends  out 
small  branches  on  all  sides. 

Sometimes  the  radicle  continues  to  enlarge  and  grow 
downward,  forming  what  is  called  a  tap-root,  from  which 
small  fibers  extend  out  into  the  soil.  Clover,  Canada 


The  Roots  of  Plants. 

A,  Erigenia,  with  tuberous  root.     It,  Buttercups,  with  fibrous  roots.    C,  White 
Clover,  with  long  tap-root  and  branches. 

thistles,  and  oak  trees,  for  example,  generally  have  such 
a  tap-root.  The  root  crops,  beets,  turnips,  carrots,  etc., 
are  simply  an  enlargement  of  the  tap-root,  which  serves 
to  store  up  food  intended  for  the  support  of  the  plant  the 
following  season. 

The  growth  of  roots  consists  mostly  of  lengthening  by 
building  on  additions  at  the  extremities.  In  this  way  the 
difficulty  of  moving  the  root  through  its  entire  length  is 
avoided,  and  every  part,  as  soon  as  formed,  is  left  in 


64 


THE  PRINCIPLES   OF   AGRICULTURE. 


undisturbed  contact  with  the  soil.  In  some  cases  the  tip 
of  the  root  is  provided  with  a  kind  of  cap,  or  shield,  to 
protect  it  from  injury  as  it  forces  its  way  through  the 
soil. 

The  Number  and  Extent  of  Roots.  —  The  process  of  sub- 
dividing and  multiplying  small  roots  goes  on  to  a  greater 
extent  than  is  generally  supposed. 
.Rich  soil  in  the  vicinity  of  the 
roots  of  some  plants  becomes  com- 
pletely filled  with  hair-like  root- 
lets. Sometimes  these  are  so 
small  as  to  require  the  aid  of  a 
microscope  to  detect  them. 

When  a  plant  is  pulled  from 
the  soil,  these  fibers  are  mostly 
broken  off,  only  the  larger  roots 
remaining  attached  to  the  stem. 

The  entire  length  of  all  the 
roots  of  a  plant  is  sometimes 
almost  incredible.  In  the  case  of 
barley,  oats,  and  wheat,  growing 

Hairs  and  root-cap  (a),  magni-    jn    rjch,    mellow    Soil,    it    lias    been 

found  that  the  total  length  of  all 

the  roots  of  one  plant  will  amount  to  from  one  hundred 
to  one  hundred  and  fifty  feet. 

Under  favorable  conditions,  roots  sometimes  descend 
to  a  great  depth.  In  deep,  mellow  soil,  the  roots  of  most 
agricultural  plants  reach  a  depth  of  several  feet.  The 
roots  of  Indian  corn,  which  in  common  soil  do  not  extend 
more  than  two  or  three  feet  below  the  surface,  have  been 
known  to  penetrate  into  the  earth  to  a  depth  of  fifteen 
feet.  Clover  roots  have  been  traced  to  a  depth  of  eight 
feet. 


Extremity  of  a  Rootlet  of 
Maple. 


PLANTS.  65 

Food  from  the  Soil.  —  The  only  substances  that  plants 
obtain  from  the  atmosphere  are  carbon,v  small  quanti- 
ties of  oxygen,  and  probably  some  nitrogen  in  the  case  of 
certain  particular  plants.  All  other  nutritive  substances, 
generally  including  nitrogen,  must  come  from  the  soil. 

A  plant  obtains  these  nourishing  substances  from  the 
soil  through  the  moisture  in  which  they  have  been  dis- 
solved. The  moisture  of  the  soil  passes  through  the 
membranous  covering  of  the  root  fibers,  and  thence  up- 
ward into  the  plant,  forming  its  sap  or  juice.  Sub- 
stances dissolved  in  this  juice  are  thus  able  to  find  their 
way  to  all  parts  of  the  plant.  In  order  to  understand  the 
rise  and  flow  of  sap,  and  the  distribution  of  nutritive  sub- 
stances, it  is  necessary  to  consider  three  principles  of 
natural  philosophy  called  diffusion,  osmose,  and  capillary 
attraction. 

1.  Diffusion.  —  Diffusion  is  the  term  applied  to  the  ten- 
dency of  different  liquids,  and  solids  dissolved  in  liquids, 
to  become  thoroughly  mixed  when  placed  together.  If 
alcohol  and  water  are  placed  together  in  the  same  vessel, 
they  quickly  mingle,  so  as  to  form  a  uniform  mixture. 
If  a  handful  of  salt  is  thrown  into  a  pail  of  water,  it  is 
quickly  dissolved,  and  evenly  distributed,  so  that  all 
parts  are  equally  salted. 

The  same  is  true  if  several  substances,  as  salt,  sugar, 
and  alum,  are  dissolved  in  the  same  water.  Each  is 
equally  distributed  as  if  no  other  were  present.  These 
facts  are  due  to  the  attraction  of  molecules  of  alcohol  for 
those  of  water,  and  the  attraction  of  molecules  of  water 
for  those  of  salt,  sugar,  etc.  The  fact  that  all  the  mole- 
cules of  water  have  equal  attraction  for  salt  causes  the 
salt  to  be  equally  distributed  between  them.  If,  in  any 
way,  some  of  the  salt  could  be  withdrawn  from  a  portion 

WINS.  AG.  — 6 


66  THE   PRINCIPLES  OE   AGRICULTURE. 

of  the  water,  some  of  the  remaining  salt  would  immedi- 
ately move  forward  and  fill  the  vacancy,  so  as  to  maintain 
an  equal  distribution. 

The  diffusion  of  water  and  sulphuric  acid  may  be  seen 
by  partially  filling  a  glass  jar  or  tube  with  water  colored 
with  blue  litmus,  and  pouring  through  a  tube,  to  the 
bottom,  water  containing  a  few  drops  of  sulphuric  acid. 
The  effect  of  the  acid  would  be  to  change  the  blue  to 
red.  Sulphuric  acid  is  heavier  than  water,  and  would 
otherwise  remain  at  the  bottom ;  but  according  to  the 
law  of  diffusion,  it  gradually  mingles  with  the  water 
above  until  the  color  of  the  whole  is  changed  to  red. 

2.  Osmose. — The  term  osmose,  from  a  Greek  word 
which  means  to  push,  is  applied  to  the  fact  that  sub- 
stances which  tend  to  mingle  by  diffusion  will  pass 
through  a  porous  partition  separating  them,  and  become 
as  thoroughly  mixed  as  if  no  partition  were  present.  If 
a  quantity  of  salt  water  and  a  quantity  of  sweetened 
water  are  separated  by  a  porous  membrane,  some  salt 
will  pass  through  the  membrane  one  way,  and  some  sugar 
the  other  way,  until  both  are  equally  distributed  through 
the  whole. 

The  same  is  true  of  other  substances  dissolved  in 
water,  and  of  different  liquids  separated  by  a  membra- 
nous partition. 

This  principle  may  be  illustrated  by  placing  in  a  blad- 
der, or  some  other  membrane,  a  small  quantity  of  colored 
alcohol,  lowering  this  into  a  glass  of  water,  and  allowing 
it  to  remain  until  the  water  becomes  colored,  showing 
that  some  of  the  alcohol  has  passed  through  the  mem- 
brane into  the  water. 

While  the  membrane,  or  other  substance,  must  be 
porous,  the  pores  may  be  very  minute.  Water,  and  sub- 


PLANTS. 


67 


The  Capillary  Curve. 


stances   dissolved   in   it,  will  find  their  way  through  a 

medium  whose  pores  are  too  small  to  be  seen,  even  with 

the  aid  of  a  microscope. 

3.   Capillary  Attraction  —  The  ^attraction  of  solids  and 

liquids  for  each  other,  in  the  case  of  solids  which  will 

dissolve,  is  shown  in  the  fact  that 

the  two  adhere  to  each  other  when 

brought  in  contact. 

If  the  edge  of  a  piece  of  glass  is 

dipped  into  water,  the  water  will 

rise   a   little   distance    upon    the 

glass,  and  when  it  is  withdrawn 

some  moisture  will  remain  upon 

it.     If  a  small  glass  tube  is  placed 

in  water,  the  attraction  between 

the  two  will  cause  the  water  to  rise  in  the  tube.     The 

smaller  the  tube,  the  higher  the  water  will  rise. 

This  principle  of  attraction  between 
solids  and  liquids,  which  causes  a  liquid 
to  pass  readily  through  the  minute  tubes 
or  pores  of  a  solid,  even  upward  against 
the  force  of  gravitation,  is  called  capillary 
attraction,  from  a  Latin  word,  capillus., 
which  means  a  hair.  The  application  is 
to  the  small,  hair-like  nature  of  the  tubes 
through  which  the  principle  works.  A 

Direct  capillarity,    familiar  example  of  capillary  attraction  is 
the  rise  of  oil  in  the  wick  of  a  lamp.     The 

attraction  of  cotton  for  oil  causes  the  oil  to  pass  rapidly 

u 1 1 ward  through  the  pores  of  the  wick. 

If  one  end  of  a  towel  is  placed  in  a  bowl  of  water,  the 

water  will  gradually  pass  along  the  cotton  or  linen  fibers 

until  the  whole  towel  is  moistened. 


68  THE  PRINCIPLES  OF  AGRICULTURE. 

Application  of  these  Principles  to  Plant  Growth.  — These 
three  principles  all  have  an  application  in  the  passage  of 
substances  into  plants  from  the  soil.  Roots  are  covered 
with  a  kind  of  membranous  coating.  The  moisture  of 
the  soil,  passing  through  this  coating,  and  upward  into 
the  plant,  saturates  the  plant,  or  completely  fills  it  with 
moisture,  by  the  force  of  capillary  attraction.  The  nutri- 
tive substances  dissolved  in  the  moisture  likewise  pass 
into  the  plant  through  its  roots. 

By  the  principle  of  diffusion,  these  substances  tend 
to  distribute  themselves  equally,  not  only  through  the 
moisture  of  the  soil  about  the  roots,  but  throughout  the 
juice  or  sap  of  the  plant. 

The  Absorbing  Power  of  Roots.  —  The  material  of  which 
the  roots  of  plants  are  composed  has  a  very  strong  at- 
traction for  water.  On  this  account,  the  moisture  of 
the  soil  is  drawn  upward  through  the  roots  into  the  stem 
and  leaves  with  considerable  force.  This  pressure,  by 
filling  all  parts  of  the  plant,  assists  in  keeping  it  in  a 
firm,  upright  position.  When  the  supply  of  moisture  is 
cut  off  by  drought,  or  by  severing  the  root,  the  plant 
withers  and  droops. 

It  has  been  found  that  this  force  is  sufficient  to  assist  in 
the  extension  of  buds  and  leaves  in  their  growth.  It  is 
supposed  to  explain  also  the  tall,  slender  growth  of  crops 
in  a  wet  season.  The  upward  pressure  of  the  moisture, 
which  is  abundantly  supplied  to  roots  in  such  a  season, 
is  sufficient  to  force  the  different  parts  of  the  plant  out 
of  their  normal  dimensions. 

The  Structure  of  Plants.  —  The  roots,  stems,  and  leaves 
of  plants,  and  in  fact  all  vegetable  substances,  are  origi- 
nally composed  of  a  great  number  of  small  cells.  These 
generally  consist  of  little  membranous  vesicles  or  bags, 


PLANTS. 


69 


Cells  from  Potato  Tuber. 
(Showing  Starch,  Grains.) 


which  are  filled  with  liquid  or  solid  matter.  The  cells 
of  a  potato  contain  little  grains  of  starch,  floating  in 
a  watery  liquid.  As  the  potato  ripens,  these  grains 
become  larger.  When  a  ripe  potato  is  boiled,  the  starch 
grains  swell  so  as  to  burst 
the  cells,  and  give  the  pota- 
to a  "  mealy  "  appearance. 
Starch  is  obtained  from 
potatoes  by  grinding  to 
break  the  cells,  and  then 
washing  out  the  starch. 

Growth  consists  in  the 
multiplication  of  these 
cells,  either  by  dividing 
the  old  cell  into  several 
new  ones,  or  by  forming 
several  new  cells  upon  the  outside  of  the  old  one. 

In  the  lower  orders  of  plants  there  are  some  that  con- 
sist of  single  cells,  each  new  cell  forming  a  separate 
plant.  Others  are  composed  of  a  number  of  these  sim- 
ple cells  loosely  attached  to  each  other. 

The  mushroom  that  grows  in  a  single  night,  ordinary 
mold,  and  the  blight  or  smut  that  sometimes  forms 
upon  corn  and  grain,  are  examples  of  plants  entirely 
composed  of  these  simple,  loose  cells. 

In  the  higher  orders  of  plants,  ripe  fruit  and  some 
other  soft,  succulent  parts,  are  also  composed  of  simple 
cells,  so  loosely  connected  as  to  be  easily  separated  from 
one  another. 

In  the  more  substantial  parts  of  most  plants,  however, 
the  cells  are  not  so  soft  and  loose,  but  are  firmly  con- 
nected together,  forming  what  is  called  vegetable  tissue. 

Cells  are  of  different  shapes  in  the  different  varieties 


70 


THE  PRINCIPLES  OF  AGRICULTURE. 


of  plants,  and  often  also  in  different  parts  of  the  same 
plant.  In  their  simplest  forms  they  are  generally  spher- 
ical, or  globular.  In  the  fiber  of  wood  they  are  long  and 
tapering,  firmly  joined  together  by  their  sides. 


Section  of  Wood. 

Lengthwise  Slice  of  Wood  from  an  Ailnnthus  glandulosa,  or  "  Tree  of  Heaven," 
highly  magnified. 

Sometimes  the  covering  of  the  ends  of  these  long  cells  is 
removed,  so  that  they  open  into  each  other,  and  form  a  con- 
tinuous tube,  through  which  the  sap  may  flow  more  freely. 
Fibers  of  cotton  and  flax  are  simply  long,  single  cells. 


PLANTS.  71 

The  Flow  of  the  Sap.  —  The  sap  is  the  moisture  of  the 
soil  which  has  passed  upward,  through  the  roots,  into 
the  plant.  The  plant  is  entirely  filled,  or  saturated, 
with  sap. 

By  the  principle  of  osmose  and  the  force  of  capillary 
attraction  the  sap  moves  partly  along  the  tubes  formed 
by  the  union  of  long  cells,  and  partly  through  the  mem- 
branes from  cell  to  cell,  until  every  part  of  the  plant  is 
filled. 

When  a  plant  has  become  saturated,  there  can  be  no 
more  flow  of  sap  until  room  has  been  made  for  more. 
The  flow  is  kept  up,  partly  by  the  growth  or  enlarge- 
ment of  the  plant,  forming  new  cells  which  need  to  be 
filled  with  moisture,  but  mostly  by  the  evaporation  of 
the  moisture  or  sap  from  the  leaves. 

Leaves  contain  a  great  number  of  minute  openings, 
particularly  on  the  under  side,  which  bring  the  air  in 
immediate  contact  with  the  sap  within.  Through  these 
openings  the  moisture  of  the  sap  is  continually  escaping 
into  the  air  by  evaporation. 

In  damp  weather  evaporation  is  slow,  and  hence  the 
upward  flow  of  sap  is  likewise  slow ;  but  in  dry  weather, 
and  especially  under  the  influence  of  the  warm  sunlight, 
it  goes  on  more  rapidly. 

The  quantity  of  water  conveyed  in  this  way  into  the 
atmosphere  is  very  large,  amounting  during  the  season 
to  many  times  the  weight  of  the  full-grown  plant.  Soil 
occupied  with  crops  is  thus  dried  much  faster  than  that 
upon  which  no  vegetation  is  growing. 

The  abundant  flow  of  sap  from  a  maple  in  the  spring 
is  due  to  the  fact  that  the  tree  is  not  only  filled  with  sap, 
but  this  is  placed  under  some  pressure  by  the  force  of 
capillary  attraction.  As  the  tree  contains  no  leaves  at 


72  THE  PRINCIPLES  OF  AGRICULTURE. 

this  season,  there  can  be  no  evaporation  to  relieve  the 
pressure.  The  sugar  of  the  sap  is  chemically  formed  in 
the  tree,  out  of  the  starchy  substances  stored  during  the 
previous  autumn.  9 

Nutrition.  —  The  nutritive  substances  which  are  de- 
signed to  serve  as  food  for  plants,  and  are  dissolved  in 
the  moisture  of  the  soil,  include  a  great  variety. 

Each  of  these  is  needed  in  nearly  all  parts  of  the  plant. 
The  most  of  them,  however,  must  undergo  chemical 
changes  before  they  are  ready  to  be  assimilated,  or  to 
enter  into  the  structure  of  the  plant.  Some  of  them 
must  first  rise  to  the  leaves  to  receive  certain  changes 
by  contact  with  the  atmosphere,  and  must  then  pass 
downward  again  to  all  points  where  they  are  required. 

The  sap  of  plants,  like  the  blood  of  animals,  furnishes 
a  medium  through  which  the  elements  of  food  may  find 
their  way  to  the  points  where  they  are  needed,  but  the 
flow  of  sap  is  riot  at  all  similar  to  the  circulation  of  the 
blood.  The  blood,  in  its  circulation,  actually  carries  sub- 
stances to  all  parts  of  the  body,  and  deposits  them  at  the 
points  of  destination,  but  there  is  no  such  complete  sys- 
tem of  conveyance  in  the  sap.  It  is  true  that  the  ele- 
ments of  plant  food  are  aided,  in  passing  from  the  soil 
into  the  plant,  by  the  upward  movement  of  the  sap ;  but 
when  once  in  the  plant  they  must  act  independently  of 
this  movement,  passing  sidewise,  downward,  and  in  every 
other  direction. 

This  is  to  be  explained  by  the  principles  of  diffusion 
and  osmose. 

As  salt,  when  dissolved  in  water,  will  extend  itself  to 
all  parts. of  the  water,  making  its  way  through  interven- 
ing membranes,  so  these  nutritive  substances  find  their 
svay  to  every  part  of  the  plant. 


PLANTS. 


73 


The  Power  of  Selection.  —  A  plant  has,  in  a  certain  sense, 
the  power  to  make  a  selection  of  its  food.  While  any 
substances  dissolved  in  the  moisture  of  the  soil  will  nat- 
urally find  their  way 
into  the  plant,  only 
such  of  these  as  are 
needed  will  be  taken 
up  and  made  use  of. 

Both  the  sap  of  tim- 
othy grass,  and  that  of 
clover,  for  instance, 
contain  silica.  The 
timothy  makes  use  of 
this  to  some  extent, 
but  clover,  having  lit- 
tle use  for  silica,  per- 
mits it  to  remain  in 
the  sap. 

It  is  believed  that, 
in  some  cases,  the 
roots  of  plants  are 
able  to  produce  chem- 
ical changes  in  some 
elements  of  soil,  and 
even  of  rocks,  with 
which  they  are  brought 

in  contact,  withdraw-  The  Essential  Partg  of  a 

ing  such  parts  as  are 
required,  and  leaving  the  remainder  in  the  soil. 

Flowers  and  Seeds.  —  In  a  general  sense,  the  aim  and 
tendency  of  plants  is  finally  to  produce  flowers,  and  then 
seeds,  which,  in  their  season,  are  to  spring  up  and  pro- 
duce similar  plants,  so  that  the  variety  may  continue 
perpetually  in  existence. 


74  THE  PRINCIPLES  OF  AGRICULTURE. 

The  essential  parts  of  a  flower  are  the  central,  or  in- 
terior organs,  by  which  the  seeds  are  formed.  These  are 
generally  surrounded  by  floral  envelopes,  called  the  calyx 
and  the  corolla,  whose  individual  leaves,  the  sepals  and 
petals,  give  the  flower  its  beauty. 

The  central  organs  are  of  two  kinds,  called  pistils  and 
stamens. 

The  pistils  contain  germs  from  which  seeds  are  formed, 
and  the  stamens  produce  a  fine  dust,  generally  of  a  yel- 
low color,  called  pollen. 

This  pollen,  falling  upon  the  pistils,  fertilizes  them, 
and  starts  the  formation  of  seeds. 

Usually  both  stamens  and  pistils  grow  upon  the  same 
plant,  and  near  each  other  in  the  same  flower.  In  some 
varieties,  however,  the  pistils  are  borne  upon  one  plant 
and  the  stamens  upon  another.  This  is  true  of  some 
varieties  of  strawberries,  and  of  hop  and  hemp  plants. 

On  account  of  this  peculiarity,  it  is  necessary,  in  culti- 
vating these  crops,  to  mix  plants  of  both  kinds. 

Sometimes  the  pistils  are  borne  upon  one  part  of  a 
plant,  and  the  stamens  upon  another.  An  example  of 
this  is  seen  in  Indian  corn.  The  pollen  produced  upon 
the  tassel  falls  upon  the  silk,  which  is  connected  with 
the  pistils  within  the  ear. 

Pollen  dust  is  produced  by  some  plants  in  large  quan- 
tities, and  is  carried  long  distances  by  the  wind.  This, 
falling  upon  different  plants  of  the  same  species,  causes 
a  mixture. 

By  a  transfer  of  pollen  dust  in  this  way,  an  almost 
endless  variety  of  some  species  of  plants  is  obtained. 
A  green  variety  of  squashes  growing  beside  a  yellow 
variety  yields  a  variety  partly  green  and  partly  yellow. 
Grains  of  pollen  dust,  carried  by  the  wind  from  one  corn- 


PLANTS.  75 

field  to  another,  will  produce  scattering  kernels  in  the 
latter  field  of  the  variety  contained  in  the  former. 


QUESTIONS, 

What  are  plants  ?  What  are  the  two  essential  parts  of  a  seed  ? 
What  is  the  embryo  ?  How  long  will  seeds  preserve  their  vitality  ? 
Why  should  new  seeds  be  used  for  planting  ?  What  is  the  effect 
of  planting  unripe  seeds?  What  is  the  effect  of  selecting  the  best 
specimens  of  seeds  for  planting  ? 

What  are  the  three  conditions  necessary  for  the  growth  of  seeds  ? 
How  much  moisture  is  most  favorable  ?  What  is  the  effect  of 
planting  seeds  in  soil  either  too  warm  or  too  cold  ?  What  is  the 
effect  of  planting  seeds  too  early  in  the  spring  ?  Why  will  seeds 
fail  to  grow  where  there  is  no  air  ?  Under  what  circumstances  is 
it  best  to  plant  seeds  deeply  ?  When  is  it  better  to  cover  them  but 
lightly  ?  What  causes  weeds  to  spring  up  after  ground  has  been 
plowed  ?  Why  have  these  weeds  failed  to  grow  before  ? 

What  are  the  three  processes  involved  in  germination  ?  Why  must 
the  seed  be  filled  with  moisture  ?  Why  is  grain  allowed  to  sprout 
in  making  malt  ?  Why  does  sprouting  produce  heat  ? 

What  are  the  radicle  and  the  plumule  ?  Why  do  they  start  from  the 
seed  in  opposite  directions  ?  Which  is  more  essential  to  the  plant, 
the  atmosphere  or  the  soil  ?  In  what  points  do  plants,  in  their 
growth,  resemble  animals  ? 

Name  the  elementary  substances  that  are  essential  to  the  growth  of 
plants.  What  food  do  plants  obtain  largely  from  the  atmosphere  ? 
Explain  the  process  by  which  it  is  obtained.  What  has  the  sun- 
light to  do  with  it  ?  Why  do  plants  become  pale  in  dark  weather  ? 
How  do  plants  purify  the  air  ?  Do  they  remove  oxygen  from  the 
air  ?  Do  they  purify  the  air  in  the  night  ?  Are  they  beneficial  to 
the  air  in  a  dwelling-house  ?  How  are  drooping  plants  revived  by 
watering?  Do  plants  obtain  nitrogen  from  the  air? 

What  are  the  purposes  of  roots  ?  Name  some  plants  which  have  tap- 
roots ?  By  what  method  do  roots  grow  ?  How  many  roots  have 
plants?  How  deep  do  they  sometimes  extend? 

Name  all  the  elements  of  food  that  plants  obtain  from  the  atmos- 
phere. Name  those  that  they  obtain  from  the  soil.  How  do  they 


76  THE  PRINCIPLES  OF  AGRICULTURE. 

obtain  food  from  the  soil?  Explain  the  principle  of  diffusion. 
What  causes  substances  to  mingle  and  dissolve  so  readily  ?  Ex- 
plain osmose.  How  are  liquids,  and  substances  dissolved  in  them, 
able  to  pass  through  a  membrane  ?  To  what  fact  is  the  term  cap- 
illary attraction  applied?  Why  is  it  so  named?  Why  will  a 
whole  towel  become  wet  if  one  end  is  placed  in  water  ?  Why  will 
water  rise  higher  in  a  very  small  tube  than  in  a  larger  one  ? 

How,  according  to  these  principles,  do  the  substances  of  the  soil  pass 
into  plants  ?  What  effect  is  produced  upon  plants  by  the  attrac- 
tion of  their  roots  for  water  ?  Why  does  a  plant  droop  when  the 
soil  becomes  too  dry  ? 

Of  what  do  the  roots,  stems,  and  leaves  of  plants  consist  ?  In  what 
way  is  growth  produced  ?  Name  some  plants  composed  of  loose 
cells.  What  is  vegetable  tissue  ?  What  is  the  form  of  cells  in 
different  plants  ? 

Explain  how  moisture  reaches  all  parts  of  the  plant  ?  What  two 
causes  tend  to  keep  up  a  continuous  flow  of  sap?  How  does  the 
moisture  of  sap  escape  into  the  atmosphere  ?  Why  does  sap  flow 
slowly  in  damp  weather?  Explain  the  cause  of  the  abundant  flow 
of  sap  from  the  maple  in  the  spring  ?  Why  does  the  flow  cease  as 
soon  as  the  leaves  begin  to  grow  ?  Does  the  flow  of  sap  resemble 
the  circulation  of  the  blood  of  animals? 

In  what  direction  do  the  nutritive  substances  move  within  the  plant  ? 
What  causes  them  to  move  ?  Can  plants  choose  their  food? 

What  is  the  natural  purpose  of  the  growth  of  plants  ?  Name  the 
different  parts  of  a  flower.  Explain  the  purpose  of  the  pistils 
and  the  stamens.  Name  some  plants  that  have  only  one  of  these 
upon  a  single  plant.  Name  some  that  have  the  two  upon  differ- 
ent parts  of  the  same  plant.  How  are  many  different  varieties 
of  the  same  species  of  plants  obtained  ?  AVhy  will  not  peas  and 
beans  mix  and  produce  new  varieties  ? 


CHAPTER  V. 

FERTILIZERS. 

Fertile  Soil  —  The  fertility  of  soil  depends  upon  its 
ability  to  supply  plants  with  all  the  elements  of  food 
which  they  require.  No  one  of  the  elementary  sub- 
stances which  have  been  enumerated  as  always  found 
in  the  composition  of  a  plant  can  be  dispensed  with. 

As  an  animal  cannot  live  or  thrive  without  a  proper 
supply  of  the  ordinary  elements  of  food,  so  a  plant  re- 
quires a  regular  supply  of  these  various  elements  from 
the  soil.  A  plant  poorly  supplied  with  potash  or  nitro- 
gen, for  instance,  would  produce  only  a  sickly  growth, 
and  if  entirely  deprived  of  these,  or  of  any  other  essen- 
tial element,  would  die. 

Fertile  soil,  therefore,  must  contain  not  only  large 
quantities  of  plant  food,  but  sufficient  quantities  of  every 
kind  of  food  which  plants  obtain  from  the  soil  to  supply 
the  wants  of  the  crop. 

So,  too,  soil  must  not  only  contain  these  elements,  but 
they  must  be  in  a  form  in  which  plants  can  make  use  of 
them.  An  acre  of  soil  may  contain  many  tons  of  nitro- 
gen or  phosphoric  acid,  and  yet  may  be  totally  unfit 
to  produce  a  crop,  because  these  cannot  be  converted 
into  suitable  forms  fast  enough  to  supply  the  amount  of 
food  required. 

The  following  list  gives  the  percentage  of  different  sub- 
stances which  may  exist  in  ordinary  dry,  fertile  soils. 

(77) 


78  THE  PRINCIPLES  OF  AGRICULTURE. 

Per  Cent 

Organic  matter  (containing  some  nitrogen)      .     .  9.3 

Phosphoric  acid 0.5 

Potassium  oxide 0.2 

Sodium  oxide 0.4 

Lime 6.0 

Sulphuric  acid 0.2 

Carbonic  acid .  4.2 

Silica 66.1 

Oxide  of  Iron 6.5 

Magnesia 0.9 

Alumina 5.5 

Chlorine  0.2 


100.0 

The  percentage  of  many  of  these  seems  small,  but  it 
amounts  to  a  large  quantity  per  acre.  One  tenth  of 
one  per  <?ent.  of  the  dry  soil  of  an  acre  would  generally 
amount  to  two  or  three  tons. 

The  quantity  of  many  of  these  substances  required  by 
crops  is  so  small  that  they  are  practically  inexhaustible. 
Of  those  substances  which  crops  require  in  larger  quanti- 
ties there  would  be  enough  to  last  many  years,  provided 
they  could  be  changed  and  made  available  as  fast  as 
required. 

The  ordinary  crop  of  wheat  raised  upon  an  acre  might 
require,  among  other  elements,  fifteen  pounds  of  phos- 
phoric acid  and  eighteen  pounds  of  potash.  If  the  en- 
tire amount  of  these  substances  naturally  contained  in 
good  soil  could  be  made  useful  as  fast  as  needed,  there 
would  be  no  lack  for  many  years. 

The  Effect  of  Agriculture.  —  In  a  state  of  nature  fer- 
tility is  naturally  maintained.  Plants  that  grow  upon 
the  soil  die  and  decay  upon  it.  Thus,  those  elements 
of  fertility  which  have  been  withdrawn  from  the  soil  by 
plants  in  their  growth  are  returned  to  it  by  their  death. 


FERTILIZERS.  79 

Tn  the  process  of  agriculture,  by  removing  crops  we 
take  away  a  quantity  of  these  elements,  year  by  year. 
If  this  is  continued,  and  nothing  is  returned  to  the  soil, 
in  the  course  of  time  it  becomes  impoverished.  The 
supply  of  plant  food  is  exhausted,  and  not  enough  is 
changed  to  an  available  form,  year  by  year,  to  produce 
a  crop. 

Land  that  is  "  run  out "  in  this  way  may  still  contain 
large  quantities  of  some  elements  of  fertility,  being  de- 
ficient only  in  a  few.  By  supplying  the  latter  we  may 
still  keep  up  the  fertility  of  the  land  for  many  years.  If, 
for  instance,  the  soil  of  a  certain  field  contains  enough 
available  nitrogen  to  support  a  crop  two  years,  enough 
phosphoric  acid  and  potash  for  five  years,  enough  lime 
for  ten  years,  and  enough  of  other  substances  for  a  longer 
period,  it  is  evident  that  after  two  years  we  must  supply 
nitrogen,  after  five  years  phosphoric  acid  and  potash, 
and  so  on,  unless  some  of  these  elements  have  been  lost 
in  the  mean  time,  or  some  have  been  added  by  natural 
causes. 

The  Soil  a  Storehouse  of  Plant  Food.  —  Ordinary  soil  ap- 
pears to  be  composed  of  simple,  inactive,  unchanging 
substances,  but  in  reality  it  is  like  a  vast  chemical  labo- 
ratory, in  which  plant  food  is  continually  prepared,  and 
either  furnished  immediately  to  the  plant  or  kept  in  store 
for  the  future. 

A  portion  of  the  rocky  or  mineral  parts  of  soil  con- 
tain substances  which,  when  they  have  been  changed  by 
chemical  action,  become  food  for  plants.  Among  the 
most  fertile  kinds  of  soil  are  those  which  have  been  pro- 
duced by  the  crumbling  and  decay  of  granite  and  lime- 
stone. Vegetable  mold,  which  results  from  the  decay 
of  plants  and  leaves,  and  which  is  found  to  a  certain  ex- 


80  THE  PRINCIPLES  OF  AGRICULTURE. 

tent  in  nearly  all  varieties  of  soil,  is  largely  composed  of 
the  elements  of  plant  food,  which  are  gradually  rendered 
available,  year  after  year. 

Chemical  action,  or  the  formation  of  plant  food  in  these 
substances,  is  checked  by  cold  weather,  but  goes  on  con- 
tinuously in  the  summer  season.  It  is  aided  by  a  proper 
supply  of  moisture  in  the  soil,  by  the  oxygen  and  car- 
bonic acid  of  the  atmosphere,  and  by  the  small  quan- 
tities of  ammonia  and  nitric  acid  which  are  brought  to 
the  soil  in  rain. 

An  application  of  fertilizers  to  the  soil  not  only  di- 
rectly supplies  the  elements  of  plant  food,  but  is  also 
useful  in  furnishing  substances  which  are  needed  to 
unite  chemically  with  other  substances  already  con- 
tained in  the  soil,  in  order  that  the  latter  may  become 
serviceable. 

When  roots  of  growing  plants  are  present,  these  nutri- 
tive substances  are  immediately  absorbed,  so  far  as  they 
are  needed.  If  formed  faster  than  needed,  the  surplus 
is  either  retained  for  future  use,  or  is  washed  away  by 
rains  and  wasted.  Some  varieties  of  soil,  particularly 
those  containing  clay  or  vegetable  mold,  are  able  to 
retain  large  quantities  of  these  elements  for  a  long  time, 
but  from  loose,  gravelly,  or  sandy  soil  they  are  easily 
washed  away. 

The  Elements  Needed  in  Fertilizers.  —  A  majority  of  the 
elements  of  fertility  are  contained  in  most  soils  in 
sufficient  quantities  to  last  many  years.  Those  which 
generally  fail  the  soonest,  and  which  we  must  aim  to 
supply  in  fertilizers,  are  nitrogen,  phosphoric  acid,  and 
potash. 

Some  peculiar  soils  may  be  wanting  in  some  other 
substance,  as  sulphur  or  lime ;  but  when  soils  begin  to 


FERTILIZERS.  81 

be  unproductive,  the  lack  of  one  or  all  of  the  three 
elements  mentioned  is  almost  universal. 

Plants  require  larger  quantities  of  these  elements  than 
of  any  other,  and  hence  they  fail  the  soonest. 

Nitrogen.  —  Nitrogen  is  an  element  both  essential  to 
plants  and  difficult  to  obtain.  While  the  air  contains 
an  abundance  of  it,  but  few  plants  can  make  use  of  it 
from  that  source.  It  is  not  generally  available  to  the 
plant  in  its  free  state,  but  in  combination  with  other 
elements. 

There  are  two  compounds  of  nitrogen  in  which  it  is 
believed  to  be  mostly  serviceable  to  plants:  they  are 
nitric  acid  and  ammonia. 

The  plant  seems  to  obtain  most  of  its  nitrogen  by  tak- 
ing up  through  its  roots  either  of  these  substances,  or 
compounds  formed  by  the  chemical  action  of  these  upon 
other  substances. 

1.  Nitric  Acid  (HN03).  —  Nitric  acid  is  formed  in 
the   soil   by   the   decay   of   organic   matter.      A  small 
quantity  of  it  also  exists  in  the  atmosphere,  some  of 
which  arises  from  the  decay  of  organic  substances,  and 
some  is  believed  to  be  produced  out  of  the  free  nitro- 
gen and  oxygen  of  the  air  by  electric  currents  passing 
through  it. 

This  acid,  either  formed  in  the  soil  or  washed  into  it 
from  the  atmosphere,  enters  the  roots  of  the  plant,  either 
directly,  or  in  the  form  of  salts,  called  nitrates,  produced 
by  its  union  with  alkaline  substances. 

2.  Ammonia  (NH3).  —  Ammonia  is  also  produced  by 
the  decomposition  of  animal  and  vegetable  matter,  from 
which,  unless  absorbed  and  retained  by  other  substances, 
it  easily  escapes  into  the  atmosphere.     It  is  very  soluble 
in  water,  and  is  absorbed  by  various  substances,  as  peat 

WINS.  AGR.  —  6 


82  THE  PRINCIPLES  OF  AGRICULTURE. 

and  decaying  vegetable  matter,  clay,  and  other  soils. 
Charcoal  will  absorb  ninety  times  its  own  bulk  of  am- 
monia gas. 

Ammonia  is  therefore  widely  diffused,  though  in  small 
quantities,  in  the  atmosphere,  in  the  land,  and  in  the 
water  of  the  earth.  It  readily  combines  with  acids,  and  in 
the  atmosphere  is  not  generally  found  in  a  free  state,  but 
combined  with  carbonic  acid,  forming  carbonate  of  am- 
monia. This  carbonate  is  dissolved  in  the  moisture  of 
the  atmosphere,  and  brought  to  the  earth,  where,  to- 
gether with  the  ammonia  already  contained  in  the  soil, 
it  adds  to  the  supply  of  nitrogenous  plant  food. 

Only  a  part  of  the  nitrogen  required  for  producing 
farm  crops  is  furnished  in  the  natural  supply  of  nitric 
acid  and  ammonia.  The  farmer  adds  to  this  supply  by 
furnishing  fertilizers  which  either  contain  these  sub- 
stances or  their  compounds,  or  which  will  produce  them 
in  the  soil  by  decay  and  chemical  changes. 

Nitrification.  —  The  vegetable  matter  which  exists  in 
ordinary  soil  in  the  form  of  decaying  grass,  leaves,  roots, 
or  stable  manure,  contains  nitrogen  combined  with  car- 
bon. In  this  condition  it  is  not  available  as  plant  food. 
By  a  peculiar  process  called  nitrification  the  nitrogen  is 
separated  and  converted  into  nitric  acid.  This  acid  again 
combines  with  bases  in  the  soil  and  forms  nitrates,  as 
nitrate  of  lime,  nitrate  of  soda,  or  nitrate  of  potash,  and 
these  are  easily  dissolved  and  readily  absorbed  by  the 
roots  of  plants.  They  are  also  easily  washed  away  from 
the  soil  and  lost  when  there  are  no  plant  roots  ready  to 
take  them  up. 

The  process  of  nitrification  is  brought  about  by  the 
growth  of  a  minute  plant.  This  plant  thrives  in  warm, 
moist  soil,  which  is  sufficiently  porous  to  admit  air,  and 


FERTILIZERS.  83 

which  contains  some  alkaline  substance.  During  the 
warm  summer  months  nitrates  are  continuously  formed 
in  this  way  to  support  plants  while  they  are  grow- 
ing most  vigorously.  Young  plants  sometimes  suffer 
from  the  want  of  nitrogen  in  the  early  spring,  before 
the  soil  becomes  sufficiently  warm  for  the  formation  of 
nitrates. 

Phosphoric  Acid  (P205).  —  Phosphoric  acid,  a  combina- 
tion of  phosphorus  and  oxygen,  is  not  found  free,  but 
in  combination  with  potash,  soda,  lime,  etc. 

It  is  very  largely  a  plant  food,  and  is  especially 
necessary  for  the  proper  ripening  of  plants  and  the 
formation  of  seeds.  Its  most  common  form  is  that  of 
phosphate  of  lime  (CaOP205).  In  this  form  it  consti- 
tutes about  one  half  the  substance  of  the  bones  of  ani- 
mals, which  are  largely  used  in  preparing  this  element 
of  fertilizers. 

Potash  (K20).  —  Potash  is  also  an  important  element 
of  fertility,  which  docs  not  exist  in  ordinary  soil  in  suf- 
ficient quantity  to  support  a  continuous  succession  of 
crops. 

It  is  generally  obtained  and  used  in  the  form  of  salts 
of  potash,  as  carbonate  of  potash  (K2C03),  chloride  of 
potash  (KC1),  etc.  Carbonate  of  potash  is  the  impor- 
tant part  of  wood  ashes.  u  New  "  land  is  generally  well 
supplied  with  potash  in  the  ashes  resulting  from  the 
burning  of  trees  and  brush. 

Artificial  Fertilizers.  —  To  supply  nitrogen,  phosphoric 
acid,  and  potash  to  the  soil,  as  well  as  certain  other 
elements  which  are  sometimes  needed,  substances  are 
either  manufactured,  or  are  obtained  in  a  natural  state 
in  different  parts  of  the  world.  To  distinguish  these 
from  ordinary  farm  manure,  which  is  the  most  common 


84  THE  PRINCIPLES  OF  AGRICULTURE. 

and  natural  fertilizer  for  the  farmer,  they  are  called 
artificial  fertilizers. 

The  materials  for  them  are  obtained  from  a  variety 
of  sources,  some  of  the  more  common  of  which  are 
as  follows :  — 

Sources  of  Nitrogen.  —  1.  Nitrate  of  soda,  or  Chili  salt- 
peter, is  extensively  obtained  in  a  natural  state  from 
some  parts  of  South  America. 

2.  Sulphate  of  ammonia  is  obtained  for  a  fertilizer 
from  "  gas  liquor,"  or  the  water  in  which  illuminating 
gas  has  been  washed.     The  ammonia  which  the  liquid 
contains  is  obtained  by  treating  it  with  sulphuric  acid, 
with  which  the  ammonia  combines. 

3.  Fish  scrap,  meat  scrap,  dried  blood,  and  all  forms 
of  animal  refuse,  are  rich  in  nitrogen,  and  are  generally 
used  for  manufacturing  fertilizers. 

Sources  of  Phosphoric  Acid.  —  1.  Bones  are  largely  com- 
posed of  phosphate  of  lime,  which  is  converted  into  an 
available  form,  called  superphosphate ,  by  an  application 
of  sulphuric  acid.  Crushed  and  ground  bones  are  also 
used  directly  as  fertilizers,  but  yield  their  phosphoric 
acid  more  slowly.  Bone-ash,  produced  by  burning  bones 
until  they  crumble  easily,  is  less  valuable  than  ground 
bones,  as  the  process  of  burning  removes  from  the  bones 
what  nitrogen  they  contain. 

2.  Bone-black,  or  charred  bone,  is  used  at  sugar  refin- 
eries for  cleansing  sugar.     After  it  becomes  useless  for 
this  purpose  it  is  treated  with  sulphuric  acid  to  convert 
its  elements  into  a  soluble  form,  and  is  then  sold  as  a 
fertilizer. 

3.  -Mineral  deposits  are  found  at  various  points  of  the 
earth  containing  a  large  percentage  of  phosphate  of  lime. 
Their  origin  is  supposed  to  have  been  an  accumulation  of 


FERTILIZERS.  85 

the  bones  of  animals  at  some  period  in  the  ancient  his- 
tory of  the  earth.  Many  of  these  deposits  are  used  as  a 
source  of  phosphoric  acid  for  fertilizers.  Those  used  in 
this  country  are  obtained  from  South  Carolina,  in  what 
is  called  "  South  Carolina  rock,"  and  from  Canada,  in  the 
form  of  a  green  mineral,  called  apatite. 

4.  By  a  process  of  manufacturing  steel  there  is  formed 
a  waste  product,  or  slag,  which  contains  phosphoric  acid. 
This  is  sometimes  used  in  preparing  fertilizers. 

Sources  of  Potash.  —  1.  Wood  ashes  contain  to  some 
extent  all  the  mineral  or  inorganic  elements  of  plant 
food,  but  are  particularly  rich  in  carbonate  of  potash. 
They  have  been  used  as  fertilizers  since  very  ancient 
times.  Until  quite  recently  they  have  served  as  the  only 
source  of  potash  for  artificial  fertilizers. 

2.  In  the  mines  of  Germany,  potash  is  obtained  in 
the  form  of  salts  of  several  varieties.  These  are  known 
as  "  German  potash  salts."  Chloride  of  potash,  com- 
monly called  "  muriate  "  of  potash,  obtained  from  this 
source,  is  largely  used  in  this  country  for  fertilizing 
purposes. 

Guano.  —  Certain  islands  off  the  western  coast  of  South 
America  have  for  centuries  been  the  haunt  of  countless 
numbers  of  sea  birds.  The  droppings  of  these  birds  con- 
stitute guano.  It  has  accumulated  in  some  places  to 
the  depth  of  from  twenty  to  fifty  feet.  The  general  ab- 
sence of  rain  in  those  regions  has  prevented  the  valuable 
elements  from  being  washed  away.  Large  quantities  of 
this  guano  are  shipped  to  different  parts  of  the  world, 
and  are  either  applied  directly  to  the  soil,  or  used  in  pre- 
paring other  commercial  fertilizers. 

Prepared  Fertilizers.  —  The  various  substances  enumer- 
ated may  be  used  singly  as  fertilizers,  or  in  combination. 


86  THE  PRINCIPLES  OF  AGRICULTURE. 

The  most  of  them  need  to  undergo  chemical  treatment  to 
render  their  elements  available.  The  work  of  preparing 
and  mixing  is  mostly  done  at  large  factories,  from  which 
the  ordinary  commercial  fertilizers  are  shipped  and  sold 
to  farmers  in  all  parts  of  the  country. 

The  aim  in  preparing  these  is  to  produce  a  mixture 
containing  the  three  elements,  nitrogen,  phosphoric  acid, 
and  potash,  in  the  proportions  in  which  they  are  needed 
for  average  soils  and  crops. 

To  meet  the  wants  of  particular  crops,  so  far  as  they 
are  understood,  special  fertilizers  are  sometimes  prepared 
and  sold  for  each  crop,  containing  the  three  elements  in 
varying  proportions. 

In  addition  to  the  substances  mentioned,  which  furnish 
the  three  most  essential  elements  of  fertilizers,  there  are 
certain  others  which  serve  some  purpose,  either  directly 
or  indirectly,  in  improving  the  fertility  of  the  soil. 

Lime  (CaO).  —  Lime,  or  oxide  of  calcium,  is  obtained 
in  large  quantities,  in  various  localities,  from  "  limestone 
quarries."  In  its  natural  state  it  is  found  combined  with 
carbonic  acid,  for  which  it  has  a  strong  attraction,  form- 
ing calcium  carbonate  (CaC03). 

Calcium  oxide,  or  quicklime,  is  obtained  by  heating  the 
calcium  carbonate  until  the  carboni'c  acid  is  driven  off. 

Quicklime  has  a  strong  attraction  for  both  carbonic 
acid  and  water.  When  exposed  to  the  atmosphere,  it 
slowly  absorbs  both  these  substances,  forming  air-slaked 
lime. .  If  brought  in  contact  with  water,  it  unites  with  it 
so  rapidly  as  to  cause  great  heat,  producing  calcium 
hydrate  (Ca02H2). 

Lime  is  beneficial  to  soil  in  various  ways :  — 

1.  It  serves  directly  as  plant  food.  All  plants  require 
a  small  quantity. 


FERTILIZERS.  87 

2.  It  combines  with,  and  decomposes,  vegetable  sub- 
stances, and  other  elements  of  the  soil,  preparing  them 
for  plant  food. 

3.  In  a  general  wayr  it  has  a  beneficial  effect  upon 
various  kinds  of  soil,  rendering  them  better  adapted  for 
agricultural  purposes. 

It  renders  heavy,  clayey  soil  more  loose  and  mellow, 
and  sandy  soil  more  compact,  so  that  it  will  retain  more 
moisture.  It  neutralizes  the  injurious  acids  of  cold, 
peaty  soil,  and  loosens  it  for  the  admission  of  warm  air. 

Many  varieties  of  soil  already  contain  lime  in  abun- 
dance, but  where  it  is  deficient,  its  application  is  often 
of  great  benefit. 

MarL  —  Marl  is  composed  of  carbonate  of  lime  mixed 
with  other  substances,  as  clayey  or  sandy  soil.  It  some- 
times contains  some  nitrogen  and  phosphoric  acid.  The 
low  places  where  it  is  found  are  supposed  to  be  the  beds 
of  ancient  lakes  which  have  dried  up.  The  deposit  has 
been  formed  by  the  accumulation  of  shell-fish  at  the  bot- 
tom of  these  lakes,  through  long  periods  of  the  ancient 
world.  Marl  is  used  as  a  fertilizer  in  regions  near  these 
beds,  where  the  expense  of  transportation  is  not  too 
great. 

Gypsum.  —  Gypsum,  or  land  plaster,  is  produced  by  a 
union  of  lime  and  sulphuric  acid,  giving  calcium  sulphate 
and  water  (CaS04  +  H2O). 

By  heating  gypsum,  the  water  is  driven  off,  leaving  the 
calcium  sulphate,  or  plaster  of  Paris. 

It  is  found  in  nature,  in  some  localities,  and  is  used  as 
a  fertilizer  where  lime  and  sulphur  are  needed.  It  is 
especially  beneficial  to  clover,  and  other  leguminous 
crops. 

Salt  (NaCl).  —  Common  salt  is  composed  of   sodium 


88  THE  PRINCIPLES  OF  AGRICULTURE. 

and  chlorine.  As  plants  contain  both  these  elements,  in 
small  quantities,  salt  is  of  some  value  as  a  fertilizer  in 
soils  where  they  are  lacking.  It  is  also  of  some  benefit 
in  preparing  plant  food  by  exerting  chemical  action  upon 
other  substances.  It  must  be  used  with  caution,  as  in 
too  large  quantities  it  is  fatal  to  vegetation. 

An  intelligent  and  economical  use  of  fertilizers  re- 
quires a  knowledge  of  four  points  :  — 
,.,  1.  What  the  Fertilizer  Contains.  —  As  the  composition 
of  substances  used  as  fertilizers  is  determined  by  chemi- 
cal analysis,  this  is  beyond  the  power  of  the  ordinary 
farmer.  The  government  generally  affords  protection 
against  the  sale  of  worthless  compounds  by  requiring 
that  the  composition  of  the  substance  exposed  for  sale 
shall  be  printed  upon  the  package,  and  by  providing  for 
chemical  tests  of  the  goods  as  they  are  found  in  the 
market. 

2.  What  the  Soil  Requires.  —  The  composition  and  con- 
dition of  soil  in  different  localities,  and  at  different  times, 
are  so  varied,  that  no  general  rule  for  the  use  of  fertil- 
izers can  be  safely  followed. 

One  field  may  require  nitrogen,  while  another  may  be 
well  supplied  with  this,  but  may  lack  phosphoric  acid, 
or  potash,  or  both.  The  use  of  a  fertilizer  in  each  field, 
containing  an  average  quantity  of  each  element,  might 
be  a  wasteful  practice. 

The  only  method  available  to  farmers  for  determining 
what  their  soil  needs  is  to  conduct  "  field  experiments," 
applying  different  fertilizers  to  different  sections,  and 
noting  the  results.  For  such  a  purpose,  the  three  ele- 
ments may  be  obtained  singly  in  "  chemicals." 

Nitrogen,  for  instance,  may  be  obtained  in  sulphate  of 
ammonia  or  nitrate  of  soda ;  phosphoric  acid,  in  ground 


FERTILIZERS.  89 

bones  or  dissolved  bone-black ;  and  potash,  in  muriate  of 
potash  or  sulphate  of  potash. 

3.  What  the   Crop   Needs.  —  The  different  crops  vary 
considerably  in  the  relative  quantity  of  the  three   ele- 
ments needed.     It  is  important  that  each  be  supplied 
with  a  fertilizer  suited  to  its  especial  wants. 

By  a  chemical  analysis  of  different  crops,  we  may  learn 
in  what  proportion  the  different  elements  of  food  are  re- 
quired in  their  formation,  and  so  may  obtain  some  idea  of 
the  proportion  in  which  these  elements  should  be  applied 
to  the  soil. 

4.  The  Amount  Required  per  Acre.  —  Economy  in  rais- 
ing crops,  as  in  raising  animals,  requires  that  they  shall 
receive  all  the  food  they  can  consume  and  properly  as- 
similate.   No  crop  can  reach  and  thus  utilize  all  the  food 
present  in  the  soil;  hence,  more  should  be  furnished 
than  enough  to  cover  the  wants  of  a  single  crop.     At  the 
same  time,  a  large  surplus  would  involve  waste,  except 
in  soils  which  are  able  to  retain  it  for  future  crops. 

Methods  of  Applying  Fertilizers. — The  valuable  elements 
of  most  prepared  fertilizers  are  largely  soluble  in  water ; 
and,  as  the  tendency  of  rain  is  to  wash  these  parts  down- 
ward, they  should  generally  be  mixed  with  the  surface 
soil. 

These  fertilizers  are  usually  so  concentrated  as  to  in- 
jure or  destroy  seeds  and  roots  when  brought  into  im- 
mediate contact  with  them.  On  this  account,  care  should 
be  taken,  in  planting,  to  place  some  soil  between  them 
jnd  the  sprouting  seed. 

It  is  wiser  to  place  them  above,  rather  than  beneath 
the  seed,  so  that  the  young  roots  may  not  be  injured, 
and  so  that  their  elements  may  be  gradually  washed 
upon  the  roots  as  needed. 


90  THE  PRINCIPLES  OF  AGRICULTURE. 

As  the  roots  of  plants  are  rapidly  extended  to  con- 
siderable distances  in  all  directions,  it  is  better,  where 
much  fertilizing  material  is  to  be  used,  to  distribute  most 
of  it  evenly  through  the  soil,  and  apply  but  little  to  the 
hill  or  drill. 

Farm  Manure.  —  The  chief  source  of  fertility,  and  that 
upon  which  farmers  mainly  depend,  is  stable  manure. 
As  it  is  generally  impossible  to  raise  good  crops  without 
supplying  some  kind  of  fertilizer  to  serve  as  plant  food, 
the  manure  of  the  farm  becomes  a  matter  of  the  greatest 
importance.  The  size  and  nature  of  the  manure  heap 
often  determine  the  profits  of  the  farm.  It  is  sometimes 
called  the  farmer's  "  gold  mine." 

Success  in  agriculture  depends  very  largely  upon  an 
understanding  of  the  nature,  the  means  of  preserving, 
and  the  proper  methods  of  applying  farm  manure. 

Its  Nature.  —  It  differs  from  the  ordinary  commercial 
fertilizers  in  three  respects :  — 

1.  It  contains  all  the  elements  of  food  required  by 
plants.  As  farm  animals  live  upon  the  crops  or  plants 
of  the  farm,  it  is  evident  that  the  manure  will  contain 
the  substances  which  come  from  these  plants,  and  of 
which  they  are  composed,  less  so  much  as  the  animal 
has  assimilated,  and  converted  into  flesh,  bones,  wool, 
milk,  etc.,  and  the  carbon  which  has  escaped  with  the 
breath. 

Only  a  small  part  of  the  elements  of  food  are  thus 
assimilated  and  retained  by  the  animal  in  digestion. 
The  amount  will  depend  upon  the  nature  of  the  animal. 
In  the  case  of  young,  growing  animals,  cows  giving 
milk,  or  sheep  producing  large  quantities  of  wool,  the 
proportion  retained  will  be  greater  than  in  the  case  of 
mature  animals  yielding  no  increase.  It  may  be  stated, 


FERTILIZERS.  91 

as  an  average,  that  from  eight  to  nine  tenths  of  the 
mammal  elements  of  the  food  of  animals  exists  in  the 
manure. 

As  the  elements  of  manure  are  the  same  as  the  ele- 
ments of  plants,  it  is  evident  that  the  manure  is  suited 
for  the  growth  of  other  plants,  in  turn,  provided  it  is  all 
preserved  and  returned  to  the  soil  without  loss  or  waste, 
and  provided  sufficient  fertilizing  material  is  added  to 
take  the  place  of  the  part  retained  by  the  animal. 

2.  It  is  less  concentrated.     A  ton  of  average  manure 
contains  only  about  25  pounds  of  plant  food.     The  re- 
maining 1,975  pounds  can  be  of  no  direct  service  as  food 
for  crops.     This  renders  it  more  expensive  to  handle, 
which  is  sometimes  a  serious  objection  where  it  must  be 
conveyed  a  long  distance. 

The  bulky  nature  of  manure,  however,  gives  it  certain 
advantages.  It  is  of  great  benefit  to  heavy  soils,  by 
making  them  mellow  and  porous  for  the  admission  of 
air,  rendering  them  drier  in  a  wet  season,  and  at  the 
same  time  enabling  them  to  retain  moisture  in  a  time 
of  drought. 

The  lack  of  some  mechanical  "  divisor,"  such  as  is 
furnished  in  common  manure,  is  a  serious  objection  to 
continuous  farming  with  artificial  fertilizers  alone.  It 
often  becomes  necessary  to  plow  in  a  crop  of  clover,  or 
some  other  bulky  substance,  in  order  to  supply  this  want. 
Without  some  treatment  of  this  kind,  soils  after  a  time 
are  liable  to  become  solid  and  compact,  and  may  suffer 
from  the  slightest  drought. 

3.  It  yields  its  supplies  of  plant  food  more  slowly.     A 
large  proportion  of  the  valuable  elements  of   ordinary 
commercial  fertilizers  is  usually  soluble,  and  immedi- 
ately available  to  plants.     Probably  from  one  half  to 


92  THE  PRINCIPLES  OF   AGRICULTURE. 

three  fourths  of  the  value  of  these  fertilizers  may  be 
obtained  in  the  first  crop  after  they  are  applied. 

In  stable  manure,  only  a  small  proportion  of  these 
elements  is  soluble  and  available  at  first.  Not  more 
than  one  fourth  of  its  value  is  ordinarily  obtained  the 
first  season.  The  remainder  must  wait  for  chemical 
action  slowly  to  reduce  it  to  available  forms. 

The  Care  of  Manure.  —  The  value  to  be  derived  from 
stable  manure  depends  largely  upon  the  care  exercised 
in  preserving  it. 

Probably  nearly  one  half  the  value  of  manure  through- 
out the  country  is  lost.  Some  loss  is,  of  course,  unavoid- 
able, but  it  may  be  largely  prevented  by  proper  care. 

There  are  three  general  sources  of  loss  :  — 

1.  Fermentation.  —  Fermentation  is  a  process  of  de- 
cay, or  decomposition,  which  organic  substances  un- 
dergo when  brought  in  contact  with  moderately  warm  air. 
The  chemical  process  consists  partly  of  oxidation,  pro- 
ducing heat.  On  this  account,  it  is  sometimes  called 
heating. 

Some  kinds  of  manure  ferment  much  more  readily  and 
rapidly  than  others. 

Sometimes,  if  the  process  is  allowed  to  continue  un- 
checked, it  will  give  to  manure  the  appearance  of  having 
been  partially  burned,  leaving  only  a  light,  unsubstantial 
mass  behind.  It  is  then  said  to  be  "  fire-fanged." 

By  fermentation  the  most  valuable  elements  of  manure 
are  converted  into  gases,  and  tend  to  escape  into  the 
atmosphere.  Nitrogen  is  converted  into  ammonia,  and 
carbon  into  carbonic  acid  gas.  The  loss  of  the  former  is 
of  far  greater  importance  than  that  of  the  latter,  since 
carbon,  which  plants  obtain  so  largely  from  the  atmos- 
phere, is  of  less  value  in  manure. 


FERTILIZERS. 

When  the  fermentation  is  going  on  rapidly,  ammonia 
is  sometimes  formed  so  fast  as  to  produce  a  strong,  pun- 
gent odor.  We  may  determine  whether  it  is  escaping  to 
some  extent  by  suspending  over  the  manure  heap  a  piece 
of  litmus  paper  in  which  the  blue  color  has  been  changed 
to  red  by  dipping  it  in  some  acid.  If  there  is  any  ammo- 
nia escaping,  it  will  gradually  restore  the  color  from  red 
to  blue. 

Slight  fermentation  would  do  no  harm,  and  in  fact 
may  be  of  some  advantage  in  converting  the  elements  of 
manure  into  available  forms,  provided  there  are  other 
substances  present  ready  to  unite  with  the  gases,  and  re- 
tain them  as  soon  as  they  are  formed,  so  as  to  prevent 
their  escape.  It  is  in  this  way  sometimes  desirable  for 
special  purposes,  as  in  compost  heaps.  Generally,  how- 
ever, it  is  to  be  avoided,  since  any  advantages  gained 
by  the  process  are  overbalanced  by  the  loss  of  escaping 
gases. 

The  ordinary  methods  of  checking  fermentation  are  :  — 

(1.)  By  mixing  the  manure  of  different  animals. 
Some  kinds  of  manure  are  slow  to  ferment.  When 
these  are  mixed  with  other  kinds,  the  fermentation  of 
the  mass  is  checked. 

(2.)  By  keeping  the  manure  heap  wet.  A  certain 
amount  of  moisture  aids  fermentation,  but  an  excess 
checks  it.  It  is  therefore  of  some  advantage  to  keep 
the  heap  .as  moist  as  possible  without  causing  loss  by 
drainage. 

(3.)  By  keeping  the  heap  trodden  down,  so  as  to 
exclude  the  air.  As  the  process  requires  the  presence 
of  the  atmosphere,  it  is  evident  that  it  may  be  largely 
prevented  by  excluding  the  air  as  much  as  possible. 

For  this  reason  it  is  often  of  great  service  to  allow 


94  THE  PRINCIPLES  OF  AGRICULTUKE. 

pigs,  or  other  animals,  to  run  upon  the  manure  heap, 
so  as  to  keep  it  in  a  compact  condition. 

2.  The  Escape  of  Liquids. — The  liquid  parts  of  manure 
contain  more  than  one  half  their  value.     It  is  important 
that  some  dry,  spongy  substance,  as  straw,  leaves,  dried 
muck,  or  dry  soil,  be  used  to  absorb  and  retain  them. 
The  nitrogen  which  serves  to  form  ammonia  by  fermen- 
tation, is  largely  contained  in  the  liquids,  and  the  pres- 
ence of  these  substances  in  some  measure  prevents  the 
escape  of  ammonia,  by  combining  with  it  or  absorbing  it. 

The  same  purpose  may  be  more  fully  accomplished  by 
applying  to  the  liquids  sulphuric  acid,  or  gypsum,  which 
is  partly  composed  of  that  acid. 

3.  Exposure  to  Rain.  —  The  liquid  parts  contained  in 
manure,  and  held  by  absorbents,  are  readily  washed  out 
by  heavy  rains.     Both  ammonia  and  nitric  acid,  the  two 
available  forms  of  nitrogen,  are  largely  lost  in  this  way, 
as  well  as  some  other  elements. 

When  manure  is  piled  in  heaps  upon  land  which  is  to 
be  cultivated,  it  is  true  that  these  elements  are  washed 
into  the  soil.  This,  however,  involves  waste,  as  the 
small  plots  beneath  the  heaps  are  too  much  overstocked 
with  these  valuable  substances  to  be  able  to  render  any 
adequate  returns  in  the  crops. 

To  prevent  waste  by  washing,  manure  should  be  kept 
under  cover ;  or,  if  exposed,  should  be  so  protected  as 
to  receive  only  a  small  amount  of  rain,  which  would  do 
no  harm. 

Methods  of  Applying  Manure.  —  Whatever  particular 
methods  are  employed  in  applying  manure  to  the  soil, 
there  are  two  general  principles  that  should  always  be 
borne  in  mind  :  — 

1.    It  should   be  applied   as  soon  as   possible.      All 


FERTILIZERS.  95 

waste,  either  by  fermenting  or  washing  from  the  heap, 
is  avoided  as  soon  as  the  manure  is  scattered  upon  or 
incorporated  with  the  soil.  By  piling  it  in  heaps,  and 
allowing  it  to  ferment,  it  may  be  rendered  more  suitable 
for  the  immediate  wants  of  certain  crops,  but  this  is  at 
the  expense  of  some  of  its  value.  When  applied  without 
such  fermentation,  it  may  be  slow  to  yield  its  elements  the 
first  season,  but  these  are  preserved  for  future  years. 

2.  It  should  be  rendered  as  fine  as  possible,  and  thor- 
oughly mixed  with  the  soil.  Those  parts  which  are  sol- 
uble at  first  may  be  washed  out,  and  distributed  evenly 
enough  for  practical  purposes,  under  any  methods ;  but 
in  order  to  secure  the  benefit  of  the  mechanical  effect 
of  mixing  the  solid  parts  with  the  soil,  and  the  chemical 
effect  produced  by  these  upon  the  soil  in  decomposition, 
it  should  in  some  way  be  finely  divided,  and  thoroughly 
mixed  with  the  soil,  so  as  to  bring  its  particles  into  con- 
tact with  as  many  particles  of  the  soil  as  possible. 

Swamp  Muck.  —  Muck  or  peat  beds  are  numerous  in 
low,  wet  places,  throughout  a  large  portion  of  the  country. 
Muck  consists  of  partially  decayed  vegetable  matter,  which 
has  accumulated  through  past  ages.  It  is  of  considerable 
value  as  a  fertilizer.  It  is  especially  rich  in  nitrogen, 
samples  often  yielding  from  one  to  three  per  cent,  of  it. 

The  fertilizing  elements  of  muck,  however,  are  in  the 
form  of  certain  acids,  or  insoluble  compounds,  which  are 
not,  in  their  natural  state,  available  to  plants.  Before  it 
can  be  of  much  service  it  must  be  treated  with  some  alka- 
line substance,  so  that  its  acids  may  be  neutralized  and 
its  elements  converted  into  available  forms. 

This  may  be  accomplished  in  three  ways :  — 

1.  By  long  continued  exposure  to  the  air.  If  taken 
from  its  bed  and  exposed  to  the  air,  it  will  be  gradually 


96  THE  PRINCIPLES   OF  AGRICULTURE. 

but  very  slowly  changed  by  contact  with  ammonia  and 
other  substances  which  exist  in  small  quantities  in  the 
atmosphere.  This  course  is  not  very  practicable,  as  sev- 
eral years  are  required  to  effect  a  complete  change. 

2.  By  mixing  it  with  some  alkaline  substance,  as  lime, 
wood  ashes,  or  some  of  the  salts  of  potash.     If  united  in 
a  compost  with  a  small  quantity  of  these  substances,  the 
desired  change  is  soon  obtained. 

3.  By  mixing  it  with  stable  manure.     This  is  a  very 
profitable  method  of  treating  it.     A  twofold  purpose  is 
accomplished :   the  manure   furnishes  the  alkaline  ele- 
ments for  the  muck,  and  the  muck  retains  those  elements 
of  the  manure  which  would  otherwise  escape  into  the  air 
by  fermentation.     For  this  purpose,  one  part  of  manure 
is  regarded  as  sufficient  for  three  parts  of  muck. 

Muck  as  an  Absorbent.  —  Muck,  like  ordinary  vegetable 
mold,  possesses  the  property  of  absorbing  large  quanti- 
ties of  water.  As  taken  from  the  swamp,  two  thirds  or 
three  fourths  of  its  weight  is  water.  In  drying,  its  bulk 
is  greatly  reduced.  This  property  renders  dried  muck 
an  excellent  absorbent  for  the  liquids  of  the  stable. 
These  liquids  are  exactly  suited  to  produce  the  proper 
changes  in  the  muck. 

Muck  may  be  profitably  applied  to  land  not  well  sup- 
plied with  humus,  or  vegetable  mold. 

The  Value  of  Muck.  —  The  elements  of  which  ordinary 
muck  is  composed  give  it  a  nominal  value  about  equal  to 
that  of  stable  manure.  Its  real  value  is  reduced,  of 
course,  by  the  labor  and  expense  of  procuring,  compost- 
ing, etc. 

There  is  a  wide  difference  in  the  quality  of  muck  from 
different  localities,  depending  upon  the  nature  of  the  sub- 
stances out  of  which  it  has  been  formed. 


FERTILIZERS.  97 

In  some  cases  it  contains  a  large  quantity  of  ordinary 
soil,  or  other  comparatively  worthless  matter.  Some 
samples  yield  three  or  four  times  as  much  nitrogen  as 
others.  Before  much  expense  is  incurred  in  procuring 
muck  from  any  particular  bed,  some  idea  of  its  value 
should  be  obtained,  either  by  chemical  analysis  or  some 
other  experiment. 

Some  idea  may  be  obtained  of  the  proportional  amount 
of  worthless  sand,  or  other  mineral  matter  which  the 
muck  contains,  by  placing  a  small  quantity  in  a  tube  or 
glass  of  water,  shaking  the  glass  thoroughly,  and,  after 
allowing  it  to  stand  for  some  time,  noting  the  quantity  of 
mineral  substances  which  settle  to  the  bottom. 

QUESTIONS. 

What  is  fertile  soil  ?  Name  the  elements  necessary  to  make  soil  fer- 
tile ?  Would  a  soil  containing  no  sulphur  be  fertile  ?  Would  scraps 
of  leather,  which  are  largely  composed  of  nitrogen,  add  to  the  pres- 
ent fertility  of  soil  ?  In  what  way  is  the  fertility  of  the  soil  naturally 
maintained?  What  is  the  effect  of  raising  crops? 

What  processes  are  going  on  in  the  soil  ?  Do  rocks  furnish  food  for 
plants  ?  What  effect  has  cold  weather  upon  the  chemical  processes 
in  the  soil  ?  What  is  the  effect  of  the  atmosphere  ?  How  do  fer- 
tilizers aid  the  chemical  action  ?  What  becomes  of  the  fertilizing 
substances  formed  in  the  soil?  Why  is  it  more  important  that 
loose  soil  should  be  always  occupied  with  vegetation  than  clayey 
or  mucky  soil  ? 

What  elements  are  most  generally  lacking  as  soil  becomes  impover- 
ished ?  Why  is  nitrogen  expensive  as  a  fertilizer  ?  In  what  forms 
docs  it  generally  become  food  for  plants  ?  Where  is  nitric  acid 
found,  and  how  is  it  produced  ?  How  is  ammonia  formed  ?  Where 
is  it  to  be  found  in  nature  ?  In  what  way  does  the  farmer  add  to 
the  natural  supply  of  nitric  acid  and  ammonia  ? 

What  is  meant  by  nitrification  ?     How  is  the  process  brought  about  ? 
What  conditions  are  necessary  ?    Why  is  the  supply  of  nitrogen 
smaller  in  the  early  spring  than  in  summer  ? 
WINS.  AGR.  —  7 


98  THE   PRINCIPLES  OF  AGRICULTURE. 

Of  what  is  phosphoric  acid  composed '?  In  what  forms  is  it  to  be 
found  ?  Of  what  special  use  is  it  to  plants  ?  Why  is  new  land 
generally  well  supplied  with  potash  ? 

What  do  artificial  fertilizers  usually  contain  V  From  what  sources  is 
nitrogen  obtained  for  these  fertilizers  ?  Name  the  different  sources 
of  phosphoric  acid.  How  is  potash  obtained  ? 

What  is  o-uano  ?  What  other  substances  are  sometimes  useful  as  fer- 
tilizers besides  those  mentioned  ?  In  what  form  is  lime  found  ? 
How  is  quicklime  produced  ?  What  is  air-slaked  lime  ?  In  what 
three  ways  does  lime  benefit  soil  ? 

What  is  marl  ?  Give  the  history  of  its  formation.  Of  what  use  is  it 
as  a  fertilizer  ? 

What  is  gypsum?  How  does  it  benefit  soil?  Is  salt  a  fertilizer, 
and  how  ? 

What  points  should  be  understood  in  order  to  make  a  proper  use 
of  fertilizers  ?  How  may  farmers  learn  what  fertilizers  contain  ? 
How  can  they  learn  what  the  soil  requires  ?  Why  does  one  crop 
need  a  different  fertilizer  from  another  ?  Why  must  soil  contain 
more  fertilizing  material  than  the  crop  uses  ?  Would  the  surplus 
be  wasted  in  a  clayey  soil  ? 

Why  should  chemical  fertilizers  be  placed  near  the  surface  of  the 
soil  ?  Why  should  they  not  be  allowed  to  come  in  contact  with 
seeds  and  roots  ?  Why  should  but  little  be  used  in  the  hill  ? 

Why  is  the  manure  heap  sometimes  called  the  farmer's  gold  mine  ? 
In  what  three  respects  does  stable  manure  differ  from  commercial 
fertilizers  ?  Why  is  it  a  complete  fertilizer  ? 

What  part  of  the  elements  of  plants  is  retained  in  digestion?  Of 
what  advantage  is  the  bulky  nature  of  manure  ?  How  does  it  ren- 
der land  more  moist  in  a  dry  time  ?  What  part  of  the  value  of 
manure  may  be  obtained  in  the  first  crop  ?  What  are  the  three 
sources  of  loss  to  which  stable  manure  is  subject? 

What  is  fermentation ?  How  is  the  heat  produced?  What  substan- 
ces are  lost  by  fermentation  ?  Why  is  fermentation  desirable  in  a 
compost  heap  ?  In  what  ways  may  it  be  partly  prevented  ? 

What  is  the  chief  advantage  of  allowing  pigs  to  run  upon  the  manure 
heap  ?  What  is  the  value  of  the  liquid  parts  of  manure  ?  What 
element  gives  them  their  chief  value  ?  What  are  the  benefits  of 
using  absorbents  in  the  stable  ? 

Of  what  special  benefit  is  gypsum  in  manure  ?    How  can  there  be  any 


FERTILIZERS.  99 

waste  from  manure  heaps  piled  upon  cultivated  land  ?  Can  there 
be  any  loss  to  manure  while  it  is  frozen?  What  two  general  points 
should  be  observed  in  the  use  of  manure  ?  Why  should  it  be  ap- 
plied to  the  land  as  soon  as  possible  ?  What  are  the  advantages  of 
rendering  it  fine? 

In  what  does  the  chief  value  of  swamp  muck  consist  ?  Why  is  it  of 
little  value  when  first  obtained  ?  In  what  three  ways  may  the  neces- 
sary changes  in  its  nature  be  brought  about  ?  Why  are  alkaline 
substances  needed  ?  Why  is  the  practice  of  mixing  it  with  stable 
manure  especially  profitable?  Why  is  it  a  good  absorbent?  Give 
some  idea  of  the  value  of  muck. 


CHAPTER  VI. 

CULTIVATION. 

Cultivation,  or  the  mechanical  handling  of  soil  for  the 
benefit  of  crops,  includes  a  large  part  of  the  labor  of 
farming. 

An  understanding  of  the  reasons  for  the  different  pro- 
cesses embraced  in  the  tillage  of  the  soil,  and  of  the 
benefits  to  be  derived  from  them,  is  essential  to  success 
in  agriculture. 

Purposes.  —  The  purposes  of  cultivation  may  be  classi- 
fied as  follows :  - 

1.  To  break  up  the  s0^7,  or  make  it  "  mellow"  so  that 
the  roots  of  plants  may  easily  penetrate  it. 

The  roots  of  a  few  varieties  of  plants  are  very  hard 
and  firm. 

Some  are  provided  with  a  sharp  point  at  the  tip,  so 
that  they  are  able  to  penetrate  hard  substances.  Quitch- 
grass  roots  will  sometimes  grow  entirely  through  a 
potato.  But  the  roots  of  most  agricultural  plants  are 
more  delicate,  and  make  their  way  with  difficulty  through 
hard  soil. 

In  poorly  cultivated  soil,  filled  with  hard  lumps,  roots 
are  found  to  occupy  the  mellow  portions,  avoiding  the 
lumps.  To  leave  the  soil  in  a  lumpy  condition  is  there- 
fore to  reduce  the  extent  of  the  feeding  ground  of  the 
plant. 
(100) 


CULTIVATION.  101 

The  depth  to  which  ro-ots  penetrate  is  largely  de- 
termined by  the  depth  to  which  the  soil  is  stirred  in 
cultivation. 

2.  To  admit  air  to  the  roots. 

Most  agricultural  plants  of  temperate  climates  will 
live  and  thrive  only  in  soil  which  is  sufficiently  porous  to 
admit  air. 

Experiments  show  that  the  roots  of  such  plants,  as 
well  as  the  foliage,  require  the  presence  of  free  oxygen. 
The  plants  either  die,  or  produce  a  feeble,  sickly  growth,  in 
compact  soil,  or  in  soil  continuously  saturated  with  water. 

There  are  exceptions,  as  in  case  of  the  cranberry  plant 
and  rice,  which  thrive  best  in  soil  completely  covered 
with  water  during  a  portion  of  the  year. 

3.  To  hasten  the  decomposition  of  the  soil,  and  the 
formation  of  plant  food. 

The  chemical  processes  in  the  soil  are  hastened  by 
exposure  to  the  air.  They  are  partly  dependent  upon  a 
supply  of  oxygen,  carbonic  acid,  etc.,  from  the  atmos- 
phere. By  loosening  the  soil,  so  as  to  admit  air,  and  by 
exposing  different  portions  of  it  to  the  surface  in  culti- 
vation, we  increase  its  fertility  by  hastening  the  forma- 
tion of  plant  food. 

The  practice  of  "  summer  fallowing,"  which  is  some- 
times followed,  consists  in  preparing  ground  for  a  future 
crop  by  plowing  and  harrowing  repeatedly,  so  as  to  ex- 
pose it  as  much  as  possible  to  the  beneficial  influences  of 
the  atmosphere. 

4.  To  mix  fertilizers  with  the  soil. 

Plants  thrive  best,  not  where  their  roots  find  pure  fer- 
tilizer in  some  spots,  and  poor  soil  in  others,  but  where 
the  two  are  so  completely  mixed  as  to  render  the  whole 
a  uniform  medium  of  rich  soil. 


102  THE  PRINCIPLES  OE  AGRICULTURE. 

The  benefit  to  be  derived  from  both  fertilizer  and  soil 
depends  partly  iipon  their  combination  with  each  other. 

5.    To  kill  weeds. 

Weeds  are  injurious  to  growing  crops  in  various  ways  : 

(1.)  By  occupying  the  soil  to  the  exclusion  of  culti- 
vated crops,  and  forming  a  shade,  depriving  them  of  the 
beneficial  influences  of  sunlight. 

(2.)  By  withdrawing  moisture  from  the  soil,  which 
is  taken  up  as  sap  and  transferred  to  the  atmosphere 
through  the  leaves.  The  amount  of  water  thus  removed 
from  the  soil,  where  weeds  are  numerous,  may  cause  a 
crop  to  suffer  from  want  of  moisture,  while  a  crop  upon  a 
neighboring  plot  free  from  weeds  will  be  amply  supplied. 

(3.)  By  withdrawing  food  from  the  soil  upon  which 
crops  would  otherwise  feed. 

The  quantity  of  available  plant  food  in  the  soil  at  any 
time  is  limited.  The  strongest,  most  vigorous,  and  quick- 
est growing  plants  are  sure  to  obtain  the  greatest  share. 
Most  agricultural  plants  are  not  so  vigorous  when  young 
as  the  ordinary  weeds.  Weeds  grow  much  faster  at  first, 
and  so  tend  to  starve  out  other  crops. 

Weeds  should  always  be  destroyed  when  young  and 
small.  If  allowed  to  grow  until  they  attain  considerable 
size,  they  damage  the  crop,  and  are  more  difficult  to  ex- 
terminate. They  are  plants,  some  varieties  of  which 
might  be  of  service  in  their  proper  places,  but  they  can- 
not be  made  useful  when  growing  in  the  midst  of  other 
crops. 

Although  returned  to  the  soil,  they  reduce  the  avail- 
able fertility  of  the  farm  by  taking  up  the  elements  of 
plant  food  and  converting  them  into  vegetable  tissue, 
some  of  which  may  require  years  to  be  again  trans- 
formed into  soluble  matter. 


CULTIVATION.  103 

6.  To  regulate  the  supply  of  moisture. 

A.  proper  degree  of  moisture  is  an  essential  condition 
for  the  growth  of  crops.  Either  too  much  or  too  little 
is  injurious. 

During  the  hot  summer  months,  however,  when  crops 
are  growing  fastest,  they  generally  suffer  more  from  a 
lack  of  moisture  than  from  an  oversupply.  In  the  case 
of  "  hoed  "  crops,  the  amount  of  moisture  in  the  soil  may 
be  increased  by  proper  cultivation. 

In  dry  weather  moisture  finds  its  way  to  the  surface 
by  capillary  attraction,  and  evaporates  rapidly.  A 
"  mulch,"  or  light  covering  of  straw,  or  leaves,  or  any 
other  substance,  keeps  the  ground  moist  by  retarding 
this  evaporation.  By  stirring  the  surface  soil  and  keep- 
ing it  light  and  porous,  a  similar  effect  is  produced,  the 
loose  soil  serving  as  a  mulch. 

Since  the  pores  in  this  soil  are  too  large  for  capillary 
action,  the  moisture  fails  to  reach  the  surface. 

7.  To  afford  particular  treatment  to  special  crops. 
There  are  some  crops  that  require  special  treatment, 

or  handling  of  the  soil  about  them,  to  insure  the  most 
successful  growth. 

Some  plants,  for  instance,  are  supposed  to  thrive  better 
when  the  soil  is  built  up  into  "  hills  "  about  them.  The 
root  crops  require  a  soil  made  mellow  to  a  great  depth. 

Plowing.  —  The  plow  has  been  regarded,  through  all 
ages  of  the  world,  as  the  characteristic  implement  of  the 
farmer.  The  first  plow  over  used  was  nothing  more  than 
a  stick  of  wood,  with  which  the  ground  was  stirred  or 
scratched.  The  history  of  the  plow  and  its  improve- 
ments corresponds  closely  to  the  history  of  civilization 
and  improvements  in  the  art  of  agriculture.  It  is  still 
an  indispensable  implement  of  tillage.  Thoroughness  of 


104  THE  PRINCIPLES  OF  AGRICULTURE. 

cultivation  and  success  in  farming  depend  largely  upon 
the  plow  and  the  use  made  of  it. 

Deep  Plowing.  —  As  a  general  rule,  ground  is  not 
plowed  to  a  sufficient  depth.  The  soil  below  that  part 
which  is  stirred  in  cultivation  is  generally  of  little  direct 
service  to  crops. 

The  subsoil  is  often  too  hard  to  allow  roots  to  pen- 
etrate it  freely.  As  it  is  buried  away  from  the  atmos- 
phere, the  chemical  changes  which  would  convert  its 
materials  into  plant  food  are  very  slow. 

By  bringing  it  to  the  surface,  and  mixing  it  with  the 
fertilizers  and  fertile  soil,  these  materials  are  made  more 
rapidly  available. 

Economy  in  farming  requires  that  large  crops  shall  be 
produced  upon  small  areas.  By  deepening  the  cultivated 
soil,  and  thus  enlarging  the  extent  of  space  and  increas- 
ing the  supplies  of  food  available  to  the  roots  of  plants, 
we  attain  this  end. 

Deep  tillage,  also,  has  much  to  do  with  regulating  the 
supply  of  moisture.  In  wet  seasons  it  affords  drainage 
by  providing  more  space  for  the  surface  water  to  pass 
into  the  porous  soil  beneath. 

In  a  time  of  drought,  as  the  roots  of  crops  have  been 
able  to  extend  themselves  more  deeply  into  the  soil,  they 
are  able  to  obtain  a  supply  of  moisture,  and  are  not  so 
much  injured  by  the  drying  of  the  surface. 

While  deep  plowing  has  these  advantages,  there  are 
some  cautions  to  be  observed.  To  plow  land  at  first 
much  deeper  than  ever  before,  would  bring  to  the  surface 
a  large  quantity  of  crude  soil.  Unless  a  great  amount 
of  fertilizer  is  applied,  this  poor  soil  is  liable  to  injure 
and  retard  the  groAvth  of  young  plants  before  their  roots 
can  penetrate  to  the  better  soil  below.  This  difficulty 


CULTIVATION.  105 

may  be  avoided  by  making  the  deepening  of  the  soil  a 
gradual  process,  plowing  each  time  a  little  deeper  than 
before. 

Some  sandy  or  alluvial  soils  are  naturally  so  loose  as 
to  admit  air  and  roots  freely.  Such  soil,  on  the  one 
hand,  is  not  so  much  in  need  of  deep  plowing ;  and,  on 
the  other  hand,  if  the  lower  portions  are  brought  to  the 
surface,  they  can  do  no  harm,  since  they  have  become 
adapted  for  plants  by  the  presence  of  air  and  the  fertil- 
izers which  have  been  washed  downward. 

It  may  not  always  be  wise  to  plow  deeply.  In  the 
varied  processes  of  cultivation,  there  may  be  occasions 
when  shallow  plowing  will,  for  the  time  being,  better 
accomplish  the  particular  end  desired  ;  as,  for  example, 
when  the  lower  soil  is  already  sufficiently  loose,  and  we 
simply  wish  to  destroy  weeds  or  mix  fertilizers  with  the 
surface  soil. 

Subsoil  Plowing.  —  The  subsoil  plow  follows  in  the  bot- 
tom of  the  furrow  made  by  the  ordinary  plow,  stirring 
the  lower  soil  and  allowing  it  to  remain  in  the  same 
position.  By  its  use  some  of  the  advantages  of  deep 
tillage  are  gained  without  the  necessity  of  bringing  the 
poor  subsoil  to  the  surface. 

The  Time  to  Plow.  —  It  is  an  important  question  at 
what  time  plowing  should  be  done ;  whether  as  long  as 
possible  before  the  seed  is  planted  or  just  before,  —  in 
the  fall  or  in  the  spring. 

There  are  two  sides  to  the  question.  After  land  is 
plowed,  and  exposed  loosely  to  the  atmosphere,  chemical 
changes  go  on  more  rapidly,  converting  the  elements  of 
fertility  into  a  soluble  form.  On  the  other  hand,  the  soil 
is  more  exposed  to  the  washing  of  rain. 

As  all  vegetation  has  been  destroyed  by  plowing,  de- 


106  THE  PRINCIPLES  OF  AGRICULTURE. 

priving  the  soil  of  the  presence  of  living  roots,  which 
would  absorb  and  hold  these  elements,  they  are  liable  to 
be  lost  as  fast  as  formed,  unless  the  soil  from  its  nature 
is  able  to  retain  them. 

In  general,  the  answer  to  the  question  will  depend 
upon  the  nature  of  the  soil,  the  climate,  and  the  particu- 
lar crop  to  be  raised. 

A  clayey  or  mucky  soil  would  be  free  from  the  objec- 
tion mentioned,  while  in  the  case  of  a  sandy  or  gravelly 
soil  the  loss  by  washing  might  be  greater  than  the  gain 
by  exposure  to  the  atmosphere. 

In  cold  climates,  where  the  ground  remains  frozen 
through  the  winter,  there  can  be  no  loss  during  this 
season,  and  plowing  in  the  fall  gives  land  the  benefit  of 
the  crumbling  and  disintegrating  effect  of  frost. 

In  climates  where  the  ground  does  not  freeze,  and 
where  rain  is  abundant  during  winter,  there  is  a  liability 
of  large  loss  both  by  washing  out  the  soluble  elements, 
and  by  washing  away  the  finest  and  richest  parts  of 
the  soil. 

For  raising  particular  crops  there  may  be  special  rea- 
sons for  plowing  in  the  fall  or  in  the  spring,  according 
to  the  special  wants  of  the  crop.  While  ground  plowed 
in  the  fall  has  received  certain  changes  from  exposure  to 
the  air  and  the  action  of  frost,  that  plowed  in  the  spring 
will  naturally  be  more  loose  and  porous. 

Harrowing.  —  Next  to  the  plow,  the  harrow  is  the  most 
important  implement  of  agriculture.  The  purpose  of 
harrowing  is  chiefly  to  pulverize  and  level  the  soil,  and 
a  thorough  performance  of  this  work  affords  all  the  gen- 
eral advantages  of  tillage.  It  prepares  the  soil  for  roots, 
admits  air,  favors  the  formation  of  plant  food,  and 
thoroughly  mixes  fertilizers  with  the  soil.  Experiments 


CULTIVATION.  107 

have  shown  that  land  well  harrowed  will  yield  better 
crop*  than  land  poorly  harrowed,  but  supplied  with  a 
greater  quantity  of  fertilizers. 

Rotting.  —  Rolling  is  a  useful  process  in  tillage  under 
certain  circumstances.  It  crushes  and  pulverizes  lumps 
of  soil  which  have  escaped  the  work  of  the  harrow. 
When  the  soil  is  very  dry  and  loose,  rolling  presses  it 
more  compactly  about  seeds,  bringing  them  moisture  by 
capillary  action,  and  hastening  their  germination  and 
growth.  It  serves  a  good  purpose  in  the  spring,  by 
pressing  into  the  soil  the  roots  of  grass  which  have  been 
thrown  out  by  the  action  of  frost.  Clayey  land,  when 
wet,  is  injured  by  rolling,  as  the  particles  of  soil  are 
pressed  too  closely  together  to  admit  air,  and  in  drying 
form  a  hard  crust  upon  the  surface. 

Cultivating.  —  The  frequent  cultivating  or  stirring  of 
the  surface  soil  between  the  rows  of  hoed  crops,  during 
the  period  of  their  active  growth,  is  beneficial,  both  by 
killing  weeds  as  soon  as  they  appear,  and  preventing 
the  loss  of  moisture.  In  every  shower  and  rain-storm 
the  particles  of  soil  are  washed  and  beaten  together  so 
compactly  as  to  cause  moisture  to  rise  to  the  surface 
by  capillary  action  and  evaporate.  By  loosening  the 
surface  soil  repeatedly,  this  is  prevented. 

As  the  rootlets  of  plants  ompletely  fill  the  soil,  ap- 
proaching very  near  to  the  surface,  this  cultivation  should 
generally  be  shallow.  While  the  surface  soil  which  is 
stirred  in  cultivation  retains  the  moisture  beneath,  it 
becomes  drier  itself  because  of  its  loose  condition. 

By  cultivating  deeply  among  crops,  we  may  prevent 
roots  from  occupying  the  upper  portions  of  the  soil,  not 
only  by  repeatedly  breaking  them,  but  by  rendering  this 
part  of  the  soil  too  dry. 


108  THE  PRINCIPLES  OF  AGRICULTURE. 

Draining.  —  The  draining  of  land,  for  the  purpose  of  re- 
moving surplus  water  in  wet  seasons  or  in  wet  places,  is 
accomplished  either  by  surface  drains  or  by  underdrains. 

Surface  drains,  or  ditches,  are  of  some  advantage  in 
removing  the  surplus  accumulation  of  water  from  the 
surface  of  the  ground.  Besides  being  unsightly  and  in- 
convenient, they  have  the  disadvantage  of  causing  some  of 
the  richer  portions  of  the  surface  soil  to  be  washed  away. 

Underdrains  are  buried  out  of  sight,  involve  no  waste, 
and  accomplish  the  purpose  more  effectually.  The  gen- 
eral advantages  to  be  gained  by  underdraining  wet  land 
are  as  follows  :  — 

1.  It  renders  the  lower  soil  available  to  roots. 

As  the  roots  of  most  agricultural  plants  cannot  live 
without  the  presence  of  oxygen,  they  cannot  occupy 
soil  which  is  completely  saturated  with  water.  Where 
the  lower  portions  of  soil  are  filled  with  water,  roots 
are  necessarily  confined  to  the  surface  soil.  By  drain- 
ing, we  afford  them  an  opportunity  to  make  their  way 
downward. 

2.  It  admits  air  to  the  lower  soil. 

From  soil  whose  pores  are  filled  with  water,  air  is,  of 
course,  excluded.  In  such  soil  the  formation  of  plant 
food  mostly  ceases.  In  a  muck  bog  the  humus  retains 
its  elements  in  an  insoluble  condition  for  centuries. 

By  draining  the  water  out  of  soil,  we  admit  air,  and 
provide  for  the  formation  of  plant  food. 

3.  It  secures  the  benefits  of  rain. 

Rain  water,  containing  nitric  acid,  ammonia,  etc.,  is  a 
source  of  fertility.  In  falling  upon  soil  that  is  already 
filled  with  water,  it  cannot  penetrate  into  the  soil,  but 
runs  away  upon  the  surface.  Thus,  the  benefits  of  the 
rain  are  lost.  Where  water  is  withdrawn  from  the  soil 


CULTIVATION. 


109 


by  drains  underneath,  falling  rain,  instead  of  flowing 
-away,  filters  through  the  soil,  and,  except  in  case  of  loose 
Sand  or  gravel,  leaves  its  fertilizing  elements  behind. 

4.  It  prevents  the  injurious  effects  of  a  drought. 

In  a  time  of  drought,  while  the  surface  soil  becomes 
very  dry,  there  is  generally  sufficient  moisture  below.  If 
the  lower  portions  have 
been  previously  satu- 
rated so  as  to  prevent 
roots  from  occupying 
them,  the  plant  is  now 
unable  to  obtain  a  sup- 
ply of  moisture,  as  its 
roots  are  surrounded 
with  the  dry  surface 
soil ;  but  if  the  surplus 
water  has  been  drained 
away,  so  that  the  roots 
have  been  able  to  make 
their  way  downward, 
when  a  drought  occurs 
the  plant  may  obtain 
its  moisture  through 
these  lower  roots. 

5.  It  renders  ivet  land  available  for  tillage. 

It  is  often  the  case  that  the  wet  lands  upon  the  farm 
are  the  richest  in  plant  food.  Many  low,  wet  places  con- 
tain an  accumulation  of  vegetable  mold,  and  other  fer- 
tile matter  washed  in  from  the  land  around  them.  By 
draining  the  water  out  of  these  places,  we  render  them 
permanent  sources  of  wealth. 

Some  farms  are  split  up  into  small,  irregular  plots,  by 
narrow  tracts  of  land,  too  wet  for  tillage.  By  draining 


Effect  of  Underdrainage. 

A,  Drain-pipe.  J?,  Point  below  which  the  soil  is 
usually  saturated.  Ct  Point  to  which  the  water 
settles  in  a  dry  time. 


110  THE  PRINCIPLES   OF  AGRICULTURE. 

these  tracts,  one  continuous  field  may  be  formed  out  of 
a  number  of  plots,  which  is  of  great  advantage  in  the 
business  of  farming. 

6.   It  increases  the  warmth  of  the  soil. 

The  evaporation  of  water  is  a  cooling  process.  It  ab- 
sorbs heat  from  the  substance  from  which  the  moisture 
escapes.  An  object  may  be  cooled  in  hot  weather  by 
covering  it  with  a  damp  cloth.  Damp  clothing  gives  the 
body  a  chill,  not  so  much  on  account  of  the  presence  of 
the  moisture  in  the  clothing,  as  from  its  evaporation  in 
drying.  So  wet  land  is  always  cool,  because,  on  account 
of  the  presence  of  water,  evaporation  is  always  going  on. 

The  warmth  of  soil  is  promoted  by  drainage,  not  only 
by  drawing  the  water  away  from  beneath,  and  preventing 
evaporation,  but  also  by  admitting  warm  air. 

Rotation  of  Crops.  —  A  knowledge  of  the  fertility  and 
cultivation  of  the  soil  is  not  complete  without  an  under- 
standing of  the  principles  involved  in  the  rotation  of 
crops,  or  an  arrangement  of  different  crops  to  occupy  the 
same  land  successively. 

It  is  a  familiar  fact,  that,  when  the  same  kind  of  crop  is 
raised  upon  land  year  after  year,  the  yield  becomes  less 
and  less ;  and  that,  where  one  crop  fails  to  yield  good  re- 
turns, another  may  flourish.  This  fact  leads  to  the  prac- 
tice of  changing  frequently  from  one  crop  to  another. 

The  advantages  of  this  practice  are  as  follows  :  — 

1.    It  makes  use  of  all  the  elements  of  plant  food. 

Different  crops  require  the  elements  in  different  pro- 
portions. It  is  not  often  that  these  elements  are  sup- 
plied by  the  soil  in  the  exact  proportion  required  by  any 
particular  crop. 

Potatoes,  for  example,  require  more  potash  than  wheat, 
and  wheat  requires  more  phosphoric  acid  than  potatoes. 


CULTIVATION. 

If  potatoes  should  be  raised  upon  the  same  land  con- 
tinuously, the  supply  of  available  potash  would  soon  be 
exhausted,  while  there  might  still  remain  in  the  soil  an 
excess  of  phosphoric  acid. 

In  order  to  continue  to  raise  potatoes  upon  this  land, 
it  would  be  necessary  to  undergo  the  expense  of  adding 
a  supply  of  potash.  At  the  same  time,  the  surplus  of 
phosphoric  acid,  for  which  the  potatoes  have  no  use, 
might  be  washed  out  of  the  soil  and  wasted.  If  some 
crop,  like  wheat,  requiring  more  phosphoric  acid  should  be 
substituted  for  potatoes,  a  good  crop  might  be  obtained, 
and  in  the  mean  time  the  decomposition  going  on  in  the 
soil  would  render  a  new  supply  of  potash  available. 

2.  It  keeps  the  land  occupied. 

Many  of  the  cultivated  crops  have  a  short  season  of 
growth.  After  they  are  harvested,  the  land  remains  un- 
occupied until  the  following  season. 

During  this  time  the  formation  of  plant  food  in  the 
soil  is  continued,  and  is  liable  to  be  lost,  as  there  are 
no  growing  crops  present  to  make  use  of  it. 

By  following  the  crop  immediately  with  some  other, 
as  winter  grain,  or  grass,  such  loss  may  be  avoided. 

3.  It  prevents  the  loss  of  substances  which  have  been 
washed  down  into  the  subsoil. 

The  roots  of  some  plants  naturally  grow  near  the  sur- 
face of  the  soil.  In  such  cases,  some  of  the  elements  of 
food  may  be  washed  down  below  the  reach  of  these  roots. 
By  following  with  a  crop  whose  roots  tend  to  penetrate 
farther  downward,  these  may  be  gathered  up  and  saved. 

Clover,  which  has  a  deep  tap-root,  will  generally  grow 
well  after  crops  having  branching  roots,  like  wheat  or 
barley;  and,  on  the  other  hand,  these  will  thrive  well 
after  clover. 


112 


THE  PRINCIPLES  OF  AGRICULTURE. 


4.  It  secures  the  varied  advantages  of  cultivating  the 
soil. 

When  land  is  continually  occupied  with  one  crop,  like 
grass,  it  may  become  too  hard  and  compact,  and  the  for- 
mation of  plant  food  may  be  checked.  By  stirring  such 
soil,  and  exposing  it  to  the  atmosphere  in  cultivation,  we 
hasten  the  chemical  changes,  and  unlock  the  supply  of 
food  which  nature  has  in  store. 

There  are  many  old  meadows  and  pastures,  regarded  as 
worn  out  and  worthless,  which,  if  subjected  to  thorough 
cultivation,  might  yield  profitable  returns. 

5.  It  prevents   the   increase   of  weeds  and  injurious 
insects. 

In  cultivating  certain  crops,  we  may  supply  conditions 
favorable  to  the  growth  of  certain  varieties  of  weeds.  If 
the  crop  is  continued  in  the  same  soil,  these  weeds  will 
naturally  increase.  Proper  management  requires  a 
change  to  some  other  crop  with  which  such  weeds  will 
not  thrive. 

It  is  well  known  that  injurious  insects,  like  the  potato 
beetle,  will  tend  to  increase  on  land  which  is  repeatedly 
occupied  by  the  particular  crop  upon  which  they  are 
accustomed  to  prey. 

The  following  are  examples  of  rotations  which  are 
sometimes  adopted :  — 


Indian  corn 
Potatoes 
Wheat    .     . 
Clover    .     . 

Clover  .  . 
Tobacco  . 
Wheat  . 


One  year. 

Wheat       .... 

One  year. 

One  year. 

Potatoes    .... 

One  year. 

One  year. 

Barley       .... 

One  year. 

'TwO  VG3/TS 

Clover  

One  year* 

Two  years. 

Cotton       .... 

One  year. 

One  year. 

Wlieat       .... 

One  year- 

One  year. 

Clover  or  peas    . 

One  year- 

CULTIVATION.  113 


QUEST  I  ONS. 

What  are  the  different  purposes  of  cultivating  the  soil  ?  What  is 
the  effect  of  leaving  land  in  a  lumpy  condition  ?  Name  all  the 
reasons  you  can  think  of  why  plants  will  not  thrive  in  hard  soil. 
Why  do  plants  obtain  more  food  in  a  loose  soil  ?  What  reasons 
can  you  give  for  mixing  fertilizers  thoroughly  with  the  soil  ? 

In  what  three  ways  do  weeds  injure  crops?  How  do  they  dry  the 
ground  ?  Why  should  they  be  destroyed  when  small  ?  Since  they 
are  not  removed  from  the  soil,  how  do  they  reduce  its  fertility  ? 

In  what  way  does  cultivation  increase  the  supply  of  moisture  ?  Give 
several  arguments  in  favor  of  deep  plowing.  Give  several  reasons 
why  roots  do  not  generally  occupy,  to  any  great  extent,  the  soil 
below  that  which  is  stirred  in  plowing. 

What  influence  has  deep  tillage  upon  the  supply  of  moisture  ?  What 
has  it  to  do  with  economy  in  farming?  Why  is  it  unwise  to  plow 
very  deeply  at  first?  What  kinds  of  soil  may  not  need  deep  plow- 
ing? What  are  the  advantages  of  subsoil  plowing? 

Name  the  arguments  in  favor  of  plowing  in  the  fall.  Give  those 
in  favor  of  plowing  in  the  spring.  What  are  the  general  con- 
clusions in  the  matter?  What  are  the  advantages  of  thorough 
harrowing  ? 

Name  all  the  reasons  you  can  think  of  why  crops  grow  better  in 
soil  thoroughly  pulverized.  What  are  the  advantages  of  rolling 
ground  ?  Under  what  circumstances  is  it  injurious  ?  What  are 
the  different  benefits  of  cultivating  hoed  crops  ?  WTiy  should  the 
ground  be  stirred  after  every  rain-storm  ?  Why  should  this  cul- 
tivation generally  be  shallow  ? 

How  may  surplus  wat^-  be  carried  away  from  a  field?  What  are 
the  disadvantages  of  surface  drains  ?  Name  the  different  advan- 
tages of  underdrains?  Why  do  roots  grow  deeper  where  drains 
are  provided  ?  Tn  what  two  ways  do  they  render  land  more  fer- 
tile ?  How  do  they  prevent  land  from  suffering  from  a  drought  ? 
How  do  they  render  soil  warmer  ? 

What  is  meant  by  a  rotation  of  crops  ?  What  are  the  advantages  of 
a  rotation  ?  Give  examples  of  rotations  sometimes  adopted. 

WINS.  AOR.  —  8 


CHAPTER  VII. 

ANIMALS. 

/rT\BE  two  forms  of  life  upon  the  earth  are  plants  and 
A  animals.  The  chief  purpose  of  vegetable  life  is  to 
supply  the  wants  of  animal  life.  The  principal  object  in 
raising  plants,  or  crops,  in  agriculture,  is  to  obtain  a 
supply  of  food  for  animals. 

A  knowledge  of  these  crops  is  not  completed  until  we 
have  considered  them  as  fed  to  animals  to  produce  meat, 
milk,  wool,  work,  etc. 

It  is  very  important  to  understand  the  nature,  the 
peculiarities,  the  best  methods  of  feeding,  and  the  proper 
care  and  management  of  our  domestic  animals. 

The  Composition  of  the  Bodies  of  Animals.  —  The  bodies 
of  animals  are  composed  of  very  nearly  the  same  ele- 
ments as  plants. 

Some  animals,  like  the  cow  or  horse,  live  mostly  upon 
vegetation,  and  are  called  herbivorous,  or  plant-eating 
animals.  Others,  like  the  cat  and  dog,  live  largely  upon 
the  flesh  of  other  animals,  and  are  called  carnivorous, 
or  flesh-eating  animals.  Some  live  partly  upon  pUnts 
and  partly  upon  animals  and  animal  products. 

But  animal  products,  as  meat,  milk,  eggs,  etc.,  are 
produced  from  vegetable  matter,  so  that  plants  are  the 
original  source  of  all  animal  food. 

The  only  substances  that  enter  into  the  bodies  of  ani- 
mals, apart  from  plants,  and  animal  products  produced 
(114) 


ANIMALS.  115 

from  plants,  are  water,  oxygen  from  the  air,  and  small 
quantities  of  mineral  matter,  such  as  salt,  lime,  pot- 
ash, etc.,  with  which  animals  must  be  supplied  when 
these  are  not  furnished  in  sufficient  quantity  in  the  regu' 
lar  food. 

The  process  of  animal  life  consists  in  converting  the 
substances  of  plants  into  the  substances  of  the  animal 
body,  or  in  making  them  serve  the  different  wants  of  the 
animal. 

The  substances  forming  the  animal  body  may  be  divided 
into  four  classes  :  — 

1.  Water.  —  Water  is  generally  the  largest  ingredient, 
comprising  from  one  third  to  two  thirds  of  the  entire 
weight.     It  is  essential  to  plants,  furnishing  a  medium 
through  which  the  elements  of  food  may  be  distributed. 
In  animals,  it  fills  a  similar  office.     It  forms  four  fifths 
of  the  blood,  and  exists  in  the  juices  throughout  all  parts 
of  the  body. 

2.  Nitrogenous  Substances.  —  Nitrogenous  substances, 
or  substances  containing   nitrogen,  are  of   first  impor- 
tance in  the  animal  body.     They  make  up  the  muscular 
tissue,  or  lean  meat,  the  nerves,  the  skin,  hair,  wool, 
feathers,  horns,  etc.     They  also  form  a  large  part  of  the 
solid  matter  in  the  blood. 

3.  Fat.  —  Fat  does  not  fill  so  important  an  office  as 
the  nitrogenous  substances.     It  does  not  make  up  the 
tissues  and  other  essential  parts  of  the  body.     It  is  al- 
ways present,  however,  in  greater  or  less  quantity.     Par- 
ticles of  fat  are  to  be  found  scattered  between  the  fibers 
of  the  muscles.     In  well-fed  animals  fat  is  also  stored  up 
in  large  quantities  beneath  the  skin,  and  about  the  bones 
and  internal  organs. 

There  are  several  varieties  of  animal  fats,  as  stearin, 


116  THE  PRINCIPLES  OF   AGRICULTURE. 

palmitin,  and.olein.  Some  of  them,  like  stearin,  are 
hard,  and  some,  like  olein,  are  either  fluids  or  are  easily 
melted. 

4.  Ash.  —  The  mineral  parts  of  the  animal  are  gener- 
ally called  the  ash,  because  they  are  incombustible,  or  re- 
main as  ashes  after  burning.  They  are  chiefly  found  in 
the  bones,  where  they  are  needed  to  give  firmness  and 
hardness.  They  are  composed  chiefly  of  phosphate  of 
lime,  carbonate  of  lime,  phosphate  of  magnesium,  and 
phosphate  of  potassium. 

The  following  table  will  give  an  idea  of  the  average 
percentage  composition  of  the  bodies  of  domestic  ani- 
mals, after  deducting  the  contents  of  the  stomach  and 
intestines :- — 

Composition  of  Bodies  of  Animals. 

Per  cent. 

Water 51.9 

Nitrogenous  matter 14.4 

Fat 30.3 

Ash   .     .  3.4 


100.0 

The  Purposes  of  Food.  —  The  different  purposes  which 
food  must  serve  in  the  animal  system  are  :  — 

1.  To  increase  the  Size  of  the  Body.  —  Mature  ani- 
mals, whose  size  and  weight  remain  constant,  require  no 
food  for  this  purpose ;  but  in  young,  growing  animals, 
and  those  passing  from  a  lean  to  a  fat  condition,  the 
gradual  increase  in  weight  must  come  from  the  food 
consumed. 

The  formation  of  animal  products,  like  milk,  must  be 
classed  under  this  head,  since  the  substances  of  which 
milk  is  composed  first  become  a  part  of  the  animal,  and 
are  then  converted  into  milk. 


ANIMALS.  117 

2.  To  repair  Waste    or    supply  Mechanical  Force.  — 
The  particles  of .  matter  of  which  the  bodies  of  animals 
are  composed  do  not  remain  fixed  and  permanent.    They 
are  constantly  being  removed  and  replaced  by  new  par- 
ticles.    After  a  time  the  particles  become  old,  and  no 
longer  useful,  and  new  particles  are  formed  from  the 
food  to  take  their  place. 

A  constant  exchange  is  thus  going  on  in  all  parts  of 
the  body,  so  that  after  a  number  of  years  a  new  body  is 
formed,  no  part  of  the  old  remaining.  The  only  excep- 
tion to  this  is  the  enamel  upon  the  teeth,  which  is  believed 
to  remain  without  change. 

This  wasting,  or  wearing  away,  of  the  substances  of 
the  body  is  increased  by  work  or  muscular  exertion. 
The  body  is  never  at  rest.  When  asleep,  or  when  per- 
fectly quiet,  the  heart  still  beats  to  force  the  blood 
through  the  body,  and  the  lungs  are  regularly  ex- 
panded to  draw  the  breath.  Every  movement  requires 
force,  and  this  force  is  supplied  either  by  food,  or  by 
particles  of  the  body  which  must  be  replaced  by  the 
food. 

The  force  that  drives  a  train  of  cars  comes  from  the 
consumption,  or  burning,  of  fuel  under  the  boiler ;  so  • 
the  force  to  produce  motions  of  the  body  is  obtained  by 
chemical  processes,  which  either  consume  the  elements  of 
food  or  particles  of  the  body  which  have  been  formed 
from  food. 

3.  To  supply  Heat.  —  The  temperature  of  the  bodies 
of  animals,  when  in  a  healthy  condition,  is  from  98°  to 
100°.     It  cannot  be  allowed  to  vary  many  degrees  from 
this  point,  for  any  considerable  time,  without  causing 
death.     In  cold  and  hot  climates,  in  winter  and  in  sum- 
mer, it  must  be  kept  constantly  the  same.     When  the 


118  THE  PRINCIPLES  OF   AGRICULTURE. 

body  becomes  too  warm,  it  is  cooled  by  the  evaporation 
of  perspiration  from  the  skin. 

As  the  air  is  generally  cooler  than  the  bodies  of  ani- 
mals, it  is  constantly  cooling  them.  To  take  the  place 
of  the  heat  thus  withdrawn,  it  is  necessary  that  a  new 
supply  be  constantly  furnished  in  the  system.  This  is 
produced  by  burning,  or  oxidizing,  a  portion  of  the  food, 
or  particles  of  the  body.  The  oxygen  for  this  process  is 
obtained  from  the  air  through  the  lungs. 

The  Composition  of  Foods.  —  The  food  of  animals  con- 
tains six  different  classes  of  substances,  as  follows  :  — 

1.  Water.  —  All  articles  of  food  contain  more  or  less 
moisture.     Hay  and  meal,  which  appear  to  be  perfectly 
dry,  contain  from  ten  to  twenty  per  cent,  water.     Succu- 
lent food,  like  green  fodder  and  roots,  may  contain  from 
seventy  to  ninety-five  per  cent,  water.    In  addition  to  that 
contained  in  the  food,  the  animal  must  drink  enough  to 
supply  the  wants  of  the  system. 

2.  Albuminoids.  —  The  albuminoids  of  food,  sometimes 
called  protein,  are  the  parts  containing  nitrogen.     They 
are  often  called  "flesh  formers."     They  serve  to  form 
the  flesh,  or  muscle,  and  the  other  nitrogenous  parts  of 
the  body. 

The  albuminoids  contain  not  only  nitrogen,  which  is 
used  in  forming  the  muscles,  but  also  other  elements  of 
an  entirely  different  nature,  which  serve  to  supply  heat 
or  force.  The  albuminoids  may  thus  be  made  to  supply 
all  the  wants  of  the  body  ;  but  to  confine  animals  to  a 
diet  composed  entirely  of  nitrogenous  food  would  be  a 
wasteful  practice.  The  albuminoids  contain  a  larger 
proportion  of  nitrogen  than  animals  require.  After  a 
sufficient  quantity  of  such  food  has  been  consumed  to 
supply  enough  nitrogen,  it  is  necessary  to  consume  an 


ANIMALS.  119 

additional  quantity  in  order  to  obtain  enough  of  those 
elements  which  supply  heat  and  force.  The  nitrogen  of 
this  second  quantity  is  wasted,  since  the  animal  has  no 
further  use  for  it.  Heat  and  force  may  be  more  econom- 
ically supplied  with  foods  containing  less  nitrogen. 

Amides  are  another  class  of  substances  containing 
nitrogen.  They  exist  to  some  extent  in  various  kinds 
of  food,  particularly  in  green  or  immature  fodder  plants, 
and  in  vegetables.  They  are  less  valuable  than  albumi- 
noids, since  their  nitrogen  cannot  be  used  to  form  the 
tissues  of  the  body.  They  can  only  serve,  like  fats  and 
carbo-hydrates,  to  produce  heat  and  force.  As  they  are 
found  only  in  small  quantities,  and  are  comparatively  of 
little  importance,  they  have  not  generally  been  distin- 
guished from  other  elements  in  making  an  analysis  of 
foods. 

Protein  is  a  term  used  to  include  both  the  albumi- 
noids and  the  amides,  or  all  parts  of  food  which  contain 
nitrogen. 

3.  Fat.  —  The  fatty  parts  of  food  correspond  to  the 
fats  of  animals.     They  are  either  oxidized  to  produce 
heat  and  mechanical  energy,  or  are  stored  up  in  the  sys- 
tem for  future  use.     They  are  the  most  valuable  class  of 
substances  for  producing  heat  and  energy.     For  these 
purposes  they  are  worth  about  twice  as  much  as  the  same 
amount  of  albuminoids.     As  they  do  not  contain  nitro- 
gen, they  cannot  be  used  in  forming  the  tissues  of  the 
body. 

4.  Carlo-hydrates.  —  The  carbo-hydrates  of  food  com- 
prise such  substances   as   starch,  sugar,  cellulose,  etc. 
They  are  composed   of  carbon,  hydrogen,  and  oxygen. 
The  term  hydrates  is  applied  to  them  from  the  Greek 
word  hudor,  meaning  water,  because  their  hydrogen  and 


120  THE  PRINCIPLES  Otf  AGRICULTURE. 

oxygen    when   separated  from  the  carbon  would  form 
water. 

They  are  either  oxidized  in  the  body  to  produce  heat 
and  energy,  or  are  converted  into  fat.  They  are  the 
least  valuable  of  the  digestible  parts  of  food.  Starch 
is  an  important  part  of  these  substances,  and  about  two 
and  one  half  parts  of  starch  are  required  to  produce  the 
same  effect  as  one  part  of  fat. 

5.  Fiber.  —  Most  kinds  of  food  contain  more  or  less 
crude    woody   fiber,   which   is   mostly   indigestible   and 
hence  has  little  value  as  food. 

6.  Ash.  —  The  mineral  substances  in  food,  or  those 
which  would  remain  as  ashes  after  burning,  are  also 
needed  by  the  animal  in  about  the  same  proportion  as 
they  exist  in  the  average  -of  the  different  varieties  of  food. 
When  animals  are  confined  to  one  particular  kind  of  food, 
some  of  these  substances  may  be  deficient.     Although 
the  amount  required  is  small,  they  cannot  be  dispensed 
with.     Animals  fed  exclusively  upon  corn  meal  some- 
times lose  the  use  of  their  legs  from  the  want  of  sufficient 
mineral  matter  to  form  bones. 

On  the  page  opposite  is  a  table  of  some  of  the  more 
common  foods,  with  their  average  percentage  composi- 
tion, as  determined  by  chemical  analysis. 

While  the  list  gives  the  average  results  from  a  large 
number  of  separate  tests,  and  must  be  approximately 
correct,  it  should  be  remembered  that  different  samples 
differ  widely  in  their  nature. 

There  would  be  a  wide  difference,  for  instance,  be- 
tween the  composition  of  early  and  late  cut  hay,  or 
between  unripe  and  mature  corn  fodder. 

While  these  figures  may  not  accurately  represent 
the  composition  of  any  particular  sample  of  food,  they 


ANIMALS. 


121 


will  serve  well  enough  as  a  general  guide  for  practical 
purposes. 

Average  Percentage  Composition  of  Articles  of  Food. 


Kinds  of  Food. 

Water. 

Ash. 

Albumi- 
noids or 
Protein. 

Fat. 

Carbo- 
hydrates. 

Fiber. 

Average  hay    .... 
Clover  hay  
Timothy  hay  .... 
Oat  straw    

11.32 
12.56 
11.07 
9.62 

5.76 
6.10 
4.06 
520 

8.51 
12.61 
6.02 
351 

2.21 

2.48 
2.16 
221 

41.38 
39.62 
45.80 
3609 

30.82 
26.63 
30.89 
4337 

Wheat  straw    .... 
Rice  straw  

6.50 
3.66 

6.96 
1071 

4.98 
468 

1.49 
1  74 

41.99 
5090 

38.08 
2831 

Corn  fodder     .... 
Fodder  corn  (green)      . 
Ensilage  (Northern  corn) 
Ensilage  (Western  corn) 
Cow-pea  vines  (dried)    . 

Indian  corn                     . 

3205 
80.98 
70.55 
80.47 
11.05 

10  10 

4.32 
1.13 
1.05 
1.35 
8.41 

1  55 

4.29 
1.62 
2.65 
1.51 
15.68 

1034 

1.24 
0.41 
0.90 
0.70 

2.87 

5.13 

35.96 
10.62 
18.84 
10.21 
42.17 

7059 

22.14 
5.23 
6.00 
5.77 
19.82 

229 

Oats    

10.94 

2.97 

11.38 

4.81 

60.05 

9.85 

Barley 

1092 

238 

12  39 

1  86 

6988 

257 

Wheat                   .     .     . 

10.54 

086 

11.80 

2.11 

72.89 

1.80 

Rice    

14.80 

0.30 

7.50 

0.50 

76.00 

0.90 

Buckwheat                .     . 

12.60 

2.00 

10.00 

2.20 

64.50 

8.70 

Peas    

14.30 

2.40 

22.40 

2.00 

52.50 

6.40 

Sorghum  (grain)  .     .     . 
Wheat  hran      .... 
Wheat  middlings      .     . 
Cotton  -seed  meal  .     .     . 
Linseed  meal  (old  process) 
Gluten  meal     .... 
Brewers'  grains  (dried) 

12.52 
12.42 
12.00 
8.33 
9.20 
9.15 
8.19 

83.1 

1.80 
5.68 
3.18 
7.25 
5.87 
0.78 
3.58 

04 

8.88 
15.03 
14.83 
42.06 
31.53 
29.88 
19.89 

04 

3.65 
3.74 
3.89 
13.24 
7.78 
tf.ll 
5.56 

71.27 
54.17 
61.55 
23.43 
36  34 
52.62 
5175 

11.8 

1.88 
8.96 
4.55 
6.69 
9.28 
1.46 
11.03 

4.3 

891 

1  0 

06 

01 

6.5 

27 

Potatoes  

75.0 

0.9 

21 

0.2 

20.7 

1.1 

Turnips                       .     • 

920 

07 

1.1 

0.1 

6.3 

0.8 

Beets  (sugar)  .... 
Milk    

87.0 

87.5 

0.9 
0.7 

2.0 
3.2 

0.1 
3.6 

9.2 
5.0 

0.8 

Skimmed  milk     .     .     . 
Buttermilk                 .     . 

90.0 
901 

0.8 
05 

3.5 
3.0 

0.7 
1.0 

5.0 

5.4 

•    • 

Whey      

92.6 

0.7 

1.0 

0.6 

5.1 

The  Value  of  Foods.  —  The  value  of  any  food  is  deter- 
mined, not  by  the  substances  which  it  contains,  but  by 


122  THE  PRINCIPLES  OF  AGRICULTURE. 

the  amount  of  these  substances  that  can  be  digested  and 
become  useful  to  the  animal. 

There  are  but  few  articles  of  food  of  which  all  the 
albuminoids,  fats,  and  carbo-hydrates  can  be  thus  di- 
gested. The  indigestible  part  is  of  no  value  for  food. 

The  table  on  the  opposite  page  gives  the  percentage  of 
digestible  albuminoids,  fats,  and  carbo-hydrates  contained 
in  the  different  articles  of  food,  and  the  value  of  one 
hundred  pounds  of  each  variety. 

In  reckoning  these  values,  the  digestible  albuminoids 
and  fats  are,  according  to  the  usual  custom,  regarded  as 
worth  4j-  cents  per  pound,  and  the  digestible  carbo- 
hydrates as  worth  -f^  of  a  cent  per  pound. 

The  results  are,  of  course,  only  relative,  and  will  vary 
according  to  the  market  value  of  the  standard  articles 
of  food  in  any  locality.  If  average  hay  is  worth  sixty- 
four  cents  per  hundred  pounds,  or  112.80  per  ton,  then 
the  other  articles  will  be  worth  the  sums  given  in  the 
table  as  compared  with  hay. 

If  in  any  locality,  or  any  year,  the  market  value  of  hay, 
corn,  oats,  or  other  articles  commonly  used,  is  greater  or 
less,  upon  the  average,  than  the  table  indicates,  then  the 
figures  for  all  the  articles  mentioned  must  be  increased 
or  diminished  accordingly. 

The  table  affords  a  general  guide  for  selecting  and  pur- 
chasing foods,  but  it  must  not  be  depended  upon  for 
great  exactness.  No  article  of  food  can,  in  reality,  have 
an  absolute  value  of  its  own.  The  true  value  of  any 
article  as  food  depends  upon  its  combination  with  other 
foods,  the  nature  of  the  animal  to  which  it  is  fed,  and  the 
purpose  to  be  accomplished.  In  order  to  make  an  intel- 
ligent selection,  it  is  necessary  to  understand  what  partic- 
ular kinds  of  food  are  needed  in  the  given  case. 


ANIMALS. 


123 


Percentage  of  Digestible  Substances  and  Value  of  100  Pounds  of  the  Food. 


Kinds  of  Food. 

Albuminoids 
or 
Protein. 

Fat. 

Carbo- 
hydrates, in- 
cluding Fiber 

Value  of 
100  Pounds. 

Average  hay      .... 
Clover  hay    

5.40 

782 

1.00 
1.49 

41.00 
4,0.25 

$0.64 
0.77 

Timothy  hay     .... 
Oat  straw      

4.G7 
1.44 

1.03 
0.66 

41.25 
42.62 

0.62 
0.47 

Wheat  straw     .... 
Rice  straw     

0.85 
1.92 

0.54 
0.52 

37.70 
40.40 

0.39 
0.46 

Corn  fodder  

300 

0.93 

40.00 

0.53 

Fodder  corn  (green)  .     . 
Ensilage  (Western  corn) 
Cow-pea  vines  (dried)     . 

Indian  corn  .... 

1.19 
1.10 
9.56 

816 

0.31 
0.53 
1.34 

436 

10.87 
10.99 
37.02 

6564 

0.16 
0.17 
0.80 

1.13 

Oats 

846 

394 

4611 

095 

Barley  

964 

1  86 

6077 

1.04 

Wheat      . 

932 

1  79 

66  52 

105 

Rice      

5.92 

042 

7071 

0.91 

Buckwheat 

7  70 

1  84 

4921 

086 

Peas     

20.20 

1.70 

54.40 

1.44 

Sorghum  (grain)    .     .     . 
Wheat  bran  

6.84 
11.72 

2.99 
2.58 

53.06 
44.66 

0.90 
1.02 

Wheat  middlings  .     .     . 
Cotton-seed  meal    .     .     . 
Linseed  meal  (old  process) 
Gluten  meal 

11.60 
35.75 

25.85 
2330 

2.68 
11.65 
7.08 
385 

48.87 
22.25 
26.52 
5092 

1.06 
2.25 
1.66 
1  63 

Brewers'  grains  (dried)    . 
Apples      

14.52 
03 

4.77 

37.41 
129 

1.20 
013 

Pumpkins      

0.4 

0.1 

7.1 

008 

Potatoes        

2  1 

02 

218 

030 

1  i 

01 

6  1 

0  11 

Milk 

32 

36 

50 

034 

Skimmed  milk  .... 
Buttermilk 

3.5 

30 

0.7 
10 

5.0 
54 

0.23 
022 

Whey        

1.0 

0.6 

5.1 

Oil 

Economy  in  Feeding.  —  There  are  two  general  precepts 
to  be  observed  in  connection  with  the  economical  feeding 
of  stock  :  — 

1.  Feed  animals  as  much  as  they  can  digest  without 
injuring  their  health. 

The  profits  of  feeding  stock  come  either  from  the 


124  THE  PRINCIPLES  OF  AGRICULTURE. 

work  which  they  are  enabled  to  perform,  or  from  growth 
and  animal  products. 

It  requires  a  certain  amount  of  food  to  maintain 
life.  If  just  enough  is  fed  to  keep  up  the  vital  pro- 
cesses of  the  animal  and  prevent  shrinkage  of  weight, 
it  is  evident  that  the  cost  of  keeping  is  absolutely  lost 
to  the  owner,  unless,  on  account  of  the  variation  of  mar- 
ket prices,  the  animal  is  to  be  worth  more  at  some 
future  time. 

Whatever  the  animal  consumes,  digests,  and  assimi- 
lates, in  excess  of  what  is  required  to  maintain  life,  will 
be  a  source  of  profit,  as  it  will  yield  either  force  for 
work  or  animal  products. 

Generally  speaking,  the  more  food  the  animal  eats  and 
digests,  the  greater  is  the  profit,  as  the  ratio  of  gain  to 
the  food  consumed  is  greater.  If  it  should  require  ten 
pounds  of  food  per  day  to  maintain  the  life  of  a  certain 
animal,  and  three  pounds  of  food  in  addition  to  produce 
a  gain  of  one  pound  of  flesh,  then  a  ration  of  thirteen 
pounds  of  food  would  produce  a  daily  gain  of  one  pound 
of  flesh.  A  ration  of  sixteen  pounds  would  produce  a 
gain  of  two  pounds  of  flesh.  In  the  former  case  the 
ratio  of  gain  to  food  is  one  to  thirteen,  and  in  the  latter 
case  one  to  eight. 

This  principle  is  limited,  however,  by  the  digestive 
power  of  the  animal.  Any  excess  of  food  above  the 
quantity  that  can  be  properly  digested  may  lead  to 
disease  and  loss. 

2.   Feed  a  balanced  ration. 

Animals  should  be  supplied  with  food,  the  composition 
of  which  is  in  proportion  to  their  needs. 

As  the  fats  and  carbo-hydrates  of  food  are  of  a  similar 
nature,  and  serve  a  similar  purpose,  it  is  customary,  for 


ANIMALS.  125 

the  sake  of  convenience,  to  class  them  together.  The 
fats  are  reckoned  as  worth  2.44  times  as  much  as  carbo- 
hydrates ;  hence,  in  combining  the  two,  we  multiply  the 
number  of  pounds  of  fat  by  2.44,  and  add  the  number  of 
pounds  of  carbo-hydrates,  giving  what  may  be  called  the 
equivalent  of  carbo-hydrates  contained  in  the  food. 

The  question  of  food  for  any  animal,  and  for  any  pur- 
pose, becomes  a  question  of  the  proper  proportion  of 
albuminoids  and  carbo-hydrates.  The  animal  needs,  for 
its  special  requirements,  a  certain  definite  proportion  of 
each. 

If  we  furnish  a  food  containing  too  large  a  proportion 
of  either  albuminoids  or  carbo-hydrates,  the  excess  of 
either  above  what  is  required  to  make  up  the  proper  pro- 
portion for  the  given  purpose  may  be  in  part  wasted,  and 
may  become  an  injury  rather  than  a  benefit  to  the  ani- 
mal. The  animal  must  consume  a  larger  quantity  of  the 
food  than  would  otherwise  be  necessary,  in  order  to  ob- 
tain the  required  quantity  of  that  substance  in  which  the 
food  is  most  deficient. 

The  Nutritive  Ratio.  —  The  nutritive  ratio  of  a  food  is 
simply  the  ratio,  or  relation,  between  the  quantity  of  di- 
gestible albuminoids,  and  of  digestible  carbo-hydrates  or 
their  equivalents,  which  it  contains.  Average  hay,  for 
instance,  contains  about  eight  times  as  much  of  digestible 
carbo-hydrates  as  of  albuminoids,  and  hence  the  nutritive 
ratio  of  the  food  is  as  1  to  8. 

The  following  tables  give  the  nutritive  ratio  of  the 
different  kinds  of  food,  and  the  number  of  pounds  of 
digestible  albuminoids  and  carbo-hydrates  which  should 
properly  be  contained  in  the  daily  ration  of  animals  un- 
der different  circumstances,  for  one  thousand  pounds  of 
live  weight.  The  quantity  for  animals  weighing  more  or 


126 


THE  PRINCIPLES  OF  AGRICULTURE. 


less  than  one  thousand  pounds  is  found  by  increasing  or 
diminishing  the  given  amounts  proportionately.  Thus,  a 
horse  weighing  twelve  hundred  pounds  should  receive 
one  fifth  more  than  the  amounts  given  for  one  thousand 
pounds. 

Albuminoids,  Equivalent  of  Carbo-hydrates,  and  Nutritive  Ratio. 


Kinds  of  Food. 

Digestible. 

Nutritive 
Ratio. 

Albuminoids. 

Carbo-hydrates 
with  Fat  x  2.44. 

Average  hay   
Clover  hay                • 

5.40 
7.82 
4.67 
1.44 
0.85 
1.92 
3.00 
1.19 
1.10 
9.56 

8.16 
8.46 
9.64 
9.32 
5.92 
7.70 
20.20 
6.84 
11.72 
11.60 
35.75 
25.85 
23.30 
14.52 

0.30 
0.40 
210 
1.10 

3.20 
3.50 
3.00 
1.00 

4344 

43.89 
43.76 
44.23 
39.02 
41.67 
42.27 
11.63 
12.28 
40.29 

76.28 
55.72 
65.31 
70.89 
71.73 
53.70 
58.55 
60.90 
50.96 
55.41 
50.68 
43.80 
60.26 
49.05 

12.90 
7.34 
22.29 
6.34 

13.78 
6.71 
7.84 
6.56 

1  to    8 
1  to     5.6 
1  to    9.4 
1  to  30.7 
1  to  45.9 
1  to  21.7 
1  to  14 
1  to    9.8 
1  to  11.2 
1  to    4.2 

to    9.3 
to    6.6 
to    6.8 
to    7.7 
to  12.1 
to    7 
to    2.9 
8.9 
1  to    4.3 
1  to    4.8 
1  to    1.4 
1  to    1.7 
1  to    2.6 
1  to    3.4 

1  to    4.3 
1  to  18.4 
1  to  10.6 
1  to    5.8 

1  to    4.3 
1  to    1.9 
1  to    26 
1  to    6.6 

Timothy  hay  

Oat  straw    

Wheat  straw  
Rice  straw  

Corn  fodder         .     .         . 

Fodder  corn  (green)     .     . 
Ensilage  (Western  corn)  . 
Cow-pea  vines  (dried)  .     . 

Indian  corn          •              . 

Oats   
Barley    « 

Wheat                            .     . 

Rice    

Buckwheat           .         • 

Peas 

Sorghum  (grain)      .     .     . 
"Wheat  bran 

Wheat  middlings     .     .     . 
Cotton-seed  meal      .     .     . 
Linseed  meal  (old  process) 
Gluten  meal     
Brewers'  grains  (dried)     . 

Apples    

Potatoes                         .     • 

Milk                      .... 

Skimmed  milk     .... 
Buttermilk                     • 

Whey     

ANIMALS. 


127 


Food  required  for  different  Animals,  for  1,000  Pounds,  live  weight. 


Digestible 

Animals  in  different 

Digestible 

Carbo-hydrates 

Nutritive 

Circumstances. 

Albuminoids. 

with  equivalent 

Ratio. 

of  Fat. 

Ibs. 

Ibs. 

Horses  in  light  work  . 

1.8 

12.6 

1  to   7 

Horses  in  heavy  work 

.        2.8 

15.5 

1  to    5.5 

Oxen  at  rest  .     . 

0.7 

8.3 

1  to  12 

Oxen  at  work    . 

2.4 

14.4 

1  to   6 

Oxen  fattening  . 

3.0 

16.5 

1  to   5.5 

Cows  in  milk 

2.5 

13.5 

1  to    5.4 

Growing  cattle  . 

1.6 

12.7 

1  to   8 

Fattening  swine 

4.0 

24.4 

1  to   6 

Fattening  sheep 

3.5 

15.6 

1  to   4.5 

Rations.  —  To  make  up  a  balanced  ration,  we  have 
simply  to  reckon  the  quantity  of  digestible  albuminoids 
and  carbo-hydrates  contained  in  a  certain  amount  of  the 
different  articles  of  food  in  question,  varying  the  quan- 
tity of  each  article  to  meet  the  wants  of  the  case. 

If,  in  making  up  a  trial  combination,  we  find  we 
have  too  large  a  proportion  of  albuminoids,  then  we 
should  increase  the  proportional  part  of  those  articles 
in  the  ration  which  are  more  largely  composed  of  carbo- 
hydrates, and  vice  versa. 

Strict  accuracy  is  not  necessary.  If  the  result  is  within 
a  fraction  of  what  is  theoretically  required,  it  is  near 
enough  for  practical  purposes. 

The  question  whether  the  ration  is  properly  balanced 
should  always  be  considered  in  making  a  combination  of 
foods.  It  is  not  always  necessary,  however,  to  follow 
the  theory  strictly.  Some  allowance  may  be  made  for 
market  prices. 

If  either  the  nitrogenous  foods  or  the  carbonaceous 
foods  are  relatively  much  cheaper  in  the  markets,  a 
larger  proportion  of  the  cheaper  class  may  be  admitted 


128 


THE  PRINCIPLES   OF  AGRICULTURE. 


into  the  ration  for  the  sake  of  economy.  The  difference 
in  cost  may  be  sufficient  to  overcome  the  loss  caused  by 
feeding  an  incorrect  ration. 

The    following    sample    rations    will    illustrate    the 
method :  — 


Ration  for  a  Cow,  weighing  1,000  Pounds,  giving  Milk. 


Daily  Ration. 

Digestible. 

Albuminoids 

Carbo-hydrates. 

English  hay,  15  Ibs.  furnishing    .... 
Ensilage   15  Ibs.  furnishing    

Ibs. 

081 
0.17 
0.72 
081 

Ibs. 
6.52 
1.84 
1.01 
3.88 

Cotton-seed  meal,  2  Ibs.  furnishing      .     . 
Wheat  middlings,  7  Ibs.  furnishing      .     . 

Total  furnished 

2.51 
2.5 

13.25 
13.5 

1  to  5.3 
1  to  5.4 

Ration  for  a  Horse,  weighing  1,200  Pounds,  at  light  Work. 


Daily  Ration. 

Digestible. 

Albuminoids. 

Carbo-hydrates. 

Timothy  hay,  10  Ibs.  furnishing      .     .     . 
Oats,                 18                                ... 
Corn,                  2       "                        ... 

Ibs. 

0.47 
1.52 
0.16 

Ibs. 

4.38 
10.03 
1.53 

2.15 

1.8 
1.8 

15.94 
13.3 
12.6 

Furnished  for  1  000  Ibs 

Required  for  1  000  Ibs 

Ratio  furnished            

1  to  7.4 
1  to  7 

ANIMALS. 


129 


Ration  for  a  Fattening  Flog,  weighing  200  Pounds. 


Daily  Ration. 

Digestible. 

Albuminoids. 

Carbo-hydrates. 

Corn  iii6a.l  5  Ibs  furnishing                  .    . 

Ibs. 
0.41 
0.21 
0.16 

Ibs. 

3.81 
0.40 
0.88 

Skimmed  milk,  6  Ibs.  furnishing      .     .     . 
Chopped  clover  hay,  2  Ibs.  furnishing.     . 

Total  furnished  

0.78 
3.90 
4.0 

5.09 
25.45 
24.4 

Furnished  for  1  000  Ibs    ... 

Required  for  1,000  Ibs  

Ratio  furnished  

1  to  6.5 
1  to  6 

Ratio  required    

Variety  of  Food.  —  In  order  that  animals  may  be 
always  kept  in  a  healthful  and  thriving  condition,  they 
should  be  supplied  with  a  variety  of  food.  Although  a 
single  kind  of  food,  or  some  particular  combination  of 
two  or  more  kinds,  may  contain  the  albuminoids  and 
carbo-hydrates  in  proper  proportion,  it  is  unwise  to  con- 
fine an  animal  to  one  special  diet  for  a  long  time.  The 
appetite  and  digestion  are  improved  by  furnishing  a 
greater  variety. 

In  computing  a  ration,  we  do  not  take  into  account 
the  mineral  substances  contained  in  it.  Although  the 
quantities  of  these  required  are  small,  they  are  essential 
to  perfect  health.  A  particular  ration  may  not  contain 
sufficient  quantities  of  all  of  these,  and  after  a  time  the 
lack  may  cause  injurious  results.  By  furnishing  a  greater 
variety,  or  changing  the  ration  frequently,  we  may  keep 
the  various  wants  of  the  animal  more  perfectly  supplied. 

The  Manurial  Value  of  Food.  —  In  selecting  food  for 
animals  upon  the  farm,  the  cost  of  the  food  and  its  value 
for  supporting  animals  are  not  the  only  points  to  be 

WINS.  AGR.  —  9 


130 


THE   PRINCIPLES   OF  AGRICULTURE. 


considered.  We  should  also  take  into  account  its  ma- 
nurial value,  or  value  as  a  fertilizer. 

Any  kind  of  food  has  a  certain  value  as  a  fertilizer, 
and  may  be  used  directly  for  that  purpose  if  it  is  not 
too  expensive. 

Cotton-seed  is  extensively  used  in  this  way  in  the  South. 

The  manurial  value,  as  in  ordinary  fertilizers,  is  de- 
termined by  the  amount  of  nitrogen,  phosphoric  acid, 
and  potash  contained. 

The  following  table  shows  the  number  of  pounds  of 
the  three  substances  contained  in  one  ton  of  each  variety 
of  food,  and  the  manurial  value  of  a  ton.  This  value  is, 
of  course,  variable,  depending  upon  the  market  value  of 
the  three  substances  for  the  locality  and  the  season. 

Manurial  Substances  in  a  Ton  of  Food,  and  their  Value. 


Kinds  of  Food. 

Nitrogen. 

Phosphoric 
Acid. 

Potash. 

Value  in 
a  Ton. 

Cotton-seed  meal      .    .    . 
Linseed  mcul 

Ibs. 
124.0 
900 

Ibs. 
59.0 
392 

Ibs. 

42.0 

29.4 

$26.66 
19.01 

Wheat  bran    
Beans 

44.0 

820 

64.6 
23.2 

29.6 
24.0 

13.69 
16.18 

Peas  

72.0 

17.6 

19.6 

13.91 

Oats   

41.2 

12.4 

9.0 

8.03 

Barley 

340 

14.6 

9.8 

7.10 

Wheat    
Indian  corn      ..... 
Buckwheat                .         . 

37.6 
33.2 

288 

16.0 
12.2 
8.8 

10.8 
7.2 
4.2 

7.84 
6.65 
5.52 

Average  hay    .    .    .    .    . 
Timothy  hay 

31.0 
31  0 

7.6 
136 

33.6 
34.4 

7.25 

7.77 

Dead  ripe  hay      .... 
Clover  hay  

24.0 
39.4 

5.8 
11.2 

10.0 
39.0 

4.80 
9.15 

Bean  straw      

200 

82 

51.8 

6.45 

Oat  straw                        . 

100 

50 

20.8 

3.04 

Wheat  straw 

96 

52 

11  6 

253 

16.0 

15.2 

66.4 

7.10 

Potatoes       .     . 

68 

36 

112 

1  94 

Turnips 

36 

12 

58 

096 

ANIMALS.  131 

Differences  in  the  quality  of  the  food  will  also  cause 
variation,  as  in  reckoning  the  feeding  value. 

The  figures  given  are  obtained  by  reckoning  the  nitro- 
gen at  sixteen  cents  per  pound,  the  phosphoric  acid 
at  eight  cents,  and  the  potash  at  five  cents. 

The  values  of  these  substances  are  reckoned  the  same, 
in  whatever  food  they  are  found.  There  is,  however, 
some  difference  in  point  of  fact,  since  in  some  articles 
of  food  they  are  in  a  more  available  condition  than  in 
others,  and  can  be  made  more  immediately  serviceable 
as  fertilizers. 

The  Value  of  Manure  from  Food.  —  To  determine  the 
real  value  of  the  manure  from  different  kinds  of  food,  a 
deduction  must  be  made  from  the  total  manurial  value 
for  certain  losses  that  occur. 

1.  We  must  deduct  the  amount  which  the  animal  re- 
moves from  the  food  in  digestion.    This  may  be  reckoned 
upon  the  average  at  fifteen  per  cent. 

2.  The  three  substances  are  not  g  nerally  so  valuable 
in  stable  manure  as  in  commercial  fertilizers,  because 
they  are  not  so  largely  available  at  first,  and  are  subject 
to  greater  losses  before  they  can  be  used  for  plant  food. 
Probably  twenty  per  cent,  should  be  deducted  on  this 
account. 

It  must  also  be  remembered  that,  in  addition  to  these 
deductions,  there  is  always  more  or  less  loss  from  fer- 
mentation and  drainage  ;  but  this  is  so  variable  that  it 
cannot  be  definitely  stated.  It  can  only  be  estimated  in 
individual  cases,  after  a  knowledge  of  the  facts  involved. 

All  articles  of  food  fed  to  stock  upon  the  farm  have 
thus  a  double  value  :  a  feeding  value,  determined  by  the 
digestible  albuminoids  and  carbo-hydrates  ;  and  a  manu- 
rial value,  determined  by  the  amount  of  nitrogen,  phos- 
phoric acid,  and  potash  in  the  manure. 


132 


THE  PRINCIPLES  OF   AGRICULTURE. 


The  following  table  gives  these  two  values  separately 
and  combined :  — 

Double  Value  of  Food,  per  Ton. 


Kinds  of  Food. 

Value  for 
Feeding. 

Value  of 
Manure. 

Double 
Value. 

Cotton-seed  meal  

$4500 

$18.13 

$63  13 

Linseed  incjil    

3320 

12.93 

46  13 

Wheat  bran 

2040 

9.31 

2971 

Peas     

2880 

9.46 

38.26 

Oats     

19.00 

5.46 

24.46 

Barley  .         

20.80 

4.83 

25.63 

Indian  corn                                    . 

2300 

4.52 

2752 

Buckwheat  

17.20 

3.75 

20.95 

Average  hay                             .    . 

1280 

493 

17  73 

Timothy  hay     

12.40 

5.28 

17.68 

Clover  hay            

1540 

622 

21  62 

Oat  straw 

940 

207 

11  47 

Corn  fodder       

10.60 

4.83 

15.43 

Potatoes            

600 

1  32 

7  32 

Turnips                        .                    . 

220 

065 

285 

The  True  Cost  of  Food.  —  In  estimating  the  real  expense 
involved  in  the  food  furnished  to  stock,  the  value  of  the 
food  as  a  source  of  fertility  to  the  farm  should  be  de- 
ducted from  its  cost  or  market  value.  The  results  will 
vary  widely  with  the  variation  in  market  prices. 

The  following  table  will  illustrate  this  point :  — 

Cost  of  Food  in  Excess  of  Value  of  Manure. 


Kinds  of  Food. 

Cost  per 
Tou. 

Value  of 
Manure. 

True  Cost 
of  Feed. 

Cotton-seed  meal  .              ... 

,$28.00 

$18.13 

$  9.87 

Linseed  meal                        . 

2900 

12.93 

16.07 

20.00 

9.31 

10.69 

Oats     .     .         

2500 

5.46 

19.54 

18.00 

4.52 

13.48 

12.00 

4.93 

7.07 

1200 

6.22 

5.78 

Oat  straw      ...         .... 

5.00 

2.07 

2.93 

ANIMALS.  133 

Digestion.  —  The  purpose  of  digestion  is  to  dissolve 
food  and  change  its  nature,  preparing  it  to  enter  the 
blood,  and  to  sustain  the  life  and  growth  of  the  body. 
As  the  food  of  plants  is  slowly  prepared  to  enter  the  sap 
by  chemical  processes  in  the  soil,  so  the  food  of  animals 
is  prepared  in  their  digestive  organs  to  enter  the  blood 
by  similar  processes,  although  much  more  rapidly. 

The  Mouth.  —  The  process  of  digestion  begins  in  the 
mouth.  The  food  is  not  only  ground  into  a  fine  condi- 
tion by  mastication, 
and  better-  prepared 
for  chemical  action, 
but  is  also  mixed  with 
the  saliva. 

This  is  a  liquid 
consisting  mostly  of 
water,  but  containing 
substances  suited  to 
produce  some  chemi- 
cal action  upon  the 

.  One  of  the  Salivary  Glands. 

food.     It  is  secreted, 

or  separated  from  the  blood,  by  a  number  of  organs 
called  glands,  situated  in  different  parts  of  the  mouth. 
As  the  blood  passes  through  these  glands,  the  saliva  is 
taken  from  it  and  poured  into  the  mouth  as  it  is  needed 
to  moisten  the  food.  It  is  formed  quite  rapidly  while 
the  animal  is  eating.  It  is  said  to  be  produced  in  the 
mouth  of  a  horse  or  an  ox,  at  such  times,  at  the  rate  of 
four  quarts  per  hour. 

The  Stomach  and  Intestines.  —  After  the  food  which  has 
been  moistened  by  the  saliva  passes  into  the  stomach,  it 
is  mixed  with  other  liquids,  which  are  withdrawn  from 
the  blood  and  poured  into  the  stomach. 


134  THE  PRINCIPLES  OF  AGRICULTURE. 

The  mixture  is  kept  constantly  in  motion  by  the  ac- 
tion of  the  muscular  walls  of  the  stomach,  until  the  food 
becomes  softened  or  dissolved.  It  then  passes  into  the 
intestines. 

The  intestines  consist  of  a  long  tube  folded  together 
so  as  to  occupy  a  small  space.  The  portion  nearest  the 
stomach  is  the  smaller  in  diameter,  and  is  called  the 
small  intestine.  The  remainder  is  larger,  and  is  called 
the  large  intestine. 

The  intestines  of  an  ox  have  an  average  length  of 
about  150  feet,  and  those  of  a  sheep  or  a  pig  of  about 
90  feet. 

In  the  intestines,  the  food  is  still  further  mixed  with 
chemical  liquids,  and  converted  into  different  forms.  As 
it  is  thus  rendered  suitable  for  nourishment,  cither  in  the 
stomach  or  the  intestines,  it  is  absorbed  by  the  mem- 
branous lining,  and  passes  through  minute  tubes  called 
the  lacteals  into  the  blood-vessels,  to  be  carried  by  the 
circulation  of  the  blood  to  all  points  of  the  system  where 
it  is  needed. 

The  Stomachs  of  Iluininants.  —  Such  animals  as  the  cow, 
the  sheep,  and  the  goat  are  called  ruminants,  because 
they  ruminate,  or  "  chew  the  cud." 

As  these  anim.als  naturally  live  upon  food  containing 
large  quantities  of  hard,  woody  fiber,  their  digestive 
system  is  different  from  that  of  other  animals  whose 
food  is  more  concentrated  and  more  easily  digested.  The 
chief  point  of  difference  is,  that,  in  addition  to  the  reg- 
ular stomach  of  other  animals,  the  ruminants  have  three 
preliminary  stomachs  in  which  coarse  food  is  prepared 
to  enter  the  stomach  proper. 

The  first  stomach,  or  paunch  (p),  into  which  coarse 
food  first  passes  as  it  is  swallowed,  is  very  large.  It  is 


ANIMALS. 


135 


several  times  as  large  as  the  other  three  stomachs  com- 
bined. In  a  large  ox  it  contains  about  sixty  gallons,  and 
occupies  nearly  the  whole  length  of  the  left  side  of  the  ab- 
domen, or  internal  cavity  of  the  body  back  of  the  lungs. 

The  second  stomach  (b)  is  in  reality  only  a  part  of  the 
first,  as  there  is  a  free  passage  connecting  the  two.  The 
membrane  lining  its  inte- 
rior is  curiously  formed  in- 
to an  arrangement  of  cells 
like  honeycomb. 

The  third  stomach  (/) 
is  provided  with  a  great 
number  of  hard,  hooked 
projections,  which  hold  the 
food  until  it  has  been  ren- 
dered fine  enough  to  pass 
through  into  the  fourth 
stomach. 

The  fourth  stomach  (<?)  is 
the  true  digesting  stomach, 
corresponding  to  the  stomach  of  the  horse  or  the  pig. 

The  gullet,  or  tube  (0)  through  which  the  food  passes 
from  the  mouth  to  the  stomach  in  swallowing,  is,  in 
ruminants,  provided  at  its  lower  end  with  a  peculiar 
canal,  by  which  the  food  as  it  is  swallowed  may  pass 
either  into  the  first  two  stomachs  on  the  one  hand,  or 
on  the  other  hand  into  the  third  stomach.  All  food  of 
a  coarse,  fibrous  nature  generally  passes  into  the  first 
two  stomachs,  but  that  which  is  fine  and  soft,  requiring 
no  further  preparation,  may  pass  at  once  into  the  third 
and  fourth  stomachs. 

Rumination.  —  Rumination,  or  the  chewing  of  the  cud, 
is  a  very  interesting  process.  As  the  first  stomach  is 


Stomach  of  a  Ruminant. 


136  THE  PRINCIPLES  OF  AGRICULTURE. 

well  filled,  partly  with  solid  food,  and  partly  with  liquids, 
a  small  quantity  of  the  food  near  the  lower  entrance  to 
the  gullet  is  floated  upward  by  the  liquid  into  the  mouth 
by  a  slight  contraction  of  the  stomach.  The  animal 
grasps  the  solid  part  in  its  mouth,  swallows  the  liquid, 
and  proceeds  to  masticate  the  food,  reducing  it  to  a  finer 
and  softer  condition.  As  this  is  again  swallowed,  such 
parts  as  are  sufficiently  fine  and  soft  pass  into  the  third 
and  fourth  stomachs,  and  the  remainder  passes  into  the 
paunch  to  be  returned  to  the  mouth  a  second  time. 

In  order  that  rumination  may  go  on,  it  is  necessary 
that  the  paunch  be  quite  well  filled,  and  that  there  shall 
be  enough  liquid  to  separate  and  float  the  solid  food 
freely. 

Ruminants,  when  supplied  with  sufficient  water,  are 
able  to  live  without  food  for  a  long  time,  as  they  are 
able  to  make  use  of  the  large  store  of  food  in  the 
paunch,  which  is  -gradually  reduced  to  a  fine  condition, 
and  passed  along  to  the  fourth  stomach  and  intestine  (c?) 
for  digestion. 

The  Blood.  —  The  blood,  in  its  circulation,  is  the  car- 
rying system  of  the  animal  body.  The  tubes  through 
which  it  passes  become  so  small  by  subdividing  that  the 
blood  is  practically  brought  in  contact  with,  and  moistens, 
all  parts  of  the  system. 

As  the  substances  formed  from  the  food  pass  from  the 
stomach  and  intestines  into  the  blood,  they  are  imme- 
diately carried  forward  with  the  current  and  distributed 
through  the  system. 

The  blood  is  forced  along  by  the  pumping  action  of 
the  heart.  On  leaving  the  heart,  it  passes  into  large 
tubes  called  arteries  (a,  a,  a).  These  soon  begin  to  sub- 
divide into  smaller  arteries,  and  these  again  into  still 


ANIMALS.  137 

smaller,  until  they  become  a  multitude  of  minute  tubes, 
called  capillaries,  passing  through  every  part  of  the  body. 
At  length  these  again  gradually  unite  in  veins  (v,  v,  v\ 
through  which  the  blood  is  returned  to  the  heart.  It  is 


Arteries,  Capillaries,  and  Veins. 

then  sent  out  through  another  set  of  tubes,  which  con- 
duct it  through  the  lungs,  where  it  is  brought  in  con- 
tact with  the  air  taken  into  the  lungs  in  breathing, 
becomes  purified,  returns  to  the  heart,  and  starts  again 
on  its  original  course. 


138  THE  PRINCIPLES  OF  AGRICULTURE. 

The  blood  consists  of  a  colorless  fluid,  containing  an 
immense  number  of  little  flattened  disks,  called  corpus- 
cles. Most  of  these  are  red,  and  give  the  blood  its  color. 

The  purpose  of  these  disks  seems  to  be  to  absorb  oxy- 
gen from  the  air  in  the  lungs,  and  carry  it  through  the 
body,  until  it  is  needed  to  oxidize  the  elements  of  food  in 
the  blood,  or  the  tissues  of  the  body. 

As  the  disks  return  from  the  lungs  they  have  a  bright 
red  color,  which  is  supposed  to  be  due  to  the  presence  of 
oxygen  that  they  have  absorbed.  On  returning  to  the 
heart,  after  passing  through  the  body,  they  assume  a 
purple  shade. 

The  elements  of  food  in  the  blood  are  burned,  or  ox- 
idized, by  uniting  with  the  oxygen  of  the  corpuscles,  pro- 
ducing animal  heat  or  force.  Particles  of  the  body  are 
also  oxidized  and  replaced  by  new  particles. 

Excretion.  —  The  blood  not  only  brings  together  food 
and  oxygen  to  produce  this  oxidation,  but  carries  away 
the  waste  products. 

When  the  carbo-hydrates  and  fats  of  food  are  burned 
in  the  system,  the  result  is  carbonic  acid  and  water. 
When  nitrogenous  substances  are  burned,  not  only  car- 
bonic acid  and  water  are  produced,  but  also  certain 
salts,  the  most  important  of  which  is  called  urea. 

Carbonic  acid  escapes  from  the  blood  partly  through 
the  skin,  but  mostly  through  the  lungs  ;  urea  and  other 
salts,  through  the  kidneys ;  and  water,  through  the  skin, 
lungs,  and  kidneys. 

The  Nature  of  Animals.  —  An  animal  upon  the  farm  may 
be  regarded  as  a  kind  of  machine,  capable  of  performing 
a  certain  amount  of  work. 

This  work  consists  in  converting  food  into  flesh,  milk, 
wool,  etc.,  or  into  mechanical  force,  for  the  service  of 


ANIMALS.  139 

man.  The  better  the  animal,  the  better  the  work 
accomplished. 

A  locomotive  engine  supplied  with  water  and  fuel  is 
able  to  draw  a  train  of  cars.  Another  engine,  more  per- 
fectly constructed,  but  supplied  with  the  same  amount  of 
fuel,  might  produce  force  enough  to  draw  a  train  much 
heavier.  The  same  is  true  in  feeding  animals.  Econ- 
omy and  profit  in  stock  husbandry  require  that  poor  ani- 
mals shall  be  discarded,  and  that  the  crops  of  the  farm 
shall  be  fed  only  to  such  as  are  able  to  render  good 
returns. 

Health.  —  The  health  or  thrift  of  animals  is  a  matter 
that  should  receive  careful  attention.  As  good  health 
promotes  comfort,  we  should  care  for  the  health  of  our 
animals  on  the  ground  of  humane  treatment.  But  the 
question  has  a  practical  bearing  also  upon  the  profits  of 
feeding.  The  more  vigorous  the  health,  the  greater  the 
returns  for  the  food.  One  animal  may  thrive  and  in- 
crease in  weight  upon  food  with  which  another,  in  less 
vigorous  health,  would  grow  poor. 

One  cow  with  the  same  food  as  another  may  produce 
much  more  milk,  on  account  of  being  in  better  health, 
and  possessing  greater  power  to  digest  food. 

Breeds.  —  By  the  law  of  heredity,  animals  tend  to  trans- 
mit to  their  young  their  own  qualities  and  peculiarities. 
It  is  therefore  important,  in  selecting  young  animals 
to  be  raised,  to  make  choice  of  those  descended  from 
animals  known  to  possess  desirable  qualities. 

The  common  pure  breeds  are  simply  families  of  ani- 
mals whose  ancestors  were  selected  for  their  excellence 
in  certain  directions. 

The  advantage  of  thoroughbred  animals  consists  in 
the  fact  that  they  possess  certain  particular  qualities  in 


140  THE  PRINCIPLES  OF  AGRICULTURE. 

a  higher  degree  than  others.  An  opportunity  is  offered 
to  choose  such  breeds  as  are  best  adapted  to  the  purpose 
required.  One  breed  of  cows  may  have  a  natural  ten- 
dency to  take  on  fat,  or  produce  beef,  while  another  will 
tend  to  produce  milk.  One  breed  of  horses  is  adapted 
for  speed,  and  another  to  draw  heavy  loads.  Some 
breeds  of  pigs  will  fatten  rapidly  while  young,  and 
others  not  until  they  become  older  and  larger. 

Economy  requires  that  we  select  such  breeds  of  the 
different  animals  as  possess  in  the  most  marked  degree 
the  peculiarities  required  for  the  special  purpose  to  which 
they  are  devoted. 

Care.  —  The  general  care  and  treatment  of  animals  is 
as  much  a  source  of  profit  as  a  matter  of  sentiment.  To 
shelter  stock  in  warm  stables  in  winter  prevents  a  loss  of 
animal  heat.  The  amount  of  food  required  to  keep  the 
body  warm  depends  largely  upon  the  question  how  fast 
the  body  is  cooled  from  without.  When  stock  is  kept  in 
tightly  built  stables,  the  warmth  from  the  body  is  not  re- 
moved by  drafts,  but  remains  to  elevate  the  temperature 
of  the  air  in  the  stable,  and  so  prevents  a  rapid  cooling 
of  the  animal. 

Food  that  is  not  needed  to  produce  animal  heat  is  free 
to  serve  other  purposes.  The  extra  food  required  to 
keep  up  the  temperature  of  a  herd  of  animals  in  a  cold 
apartment  would,  in  a  single  winter,  pay  the  cost  of  ren- 
dering the  apartment  tight  and  warm. 

Kindness.  —  There  is  profit  as  well  as  sentiment  in 
"  kindness  to  animals."  The  digestive  and  nutritive  pro- 
cesses are  largely  influenced  by  the  condition  of  the  ner- 
vous system.  Animals  which  are  disposed  to  fight  or 
annoy  each  other  will  not  thrive  so  well  as  if  kept  apart, 
or  in  more  congenial  company.  A  horse  with  an  irrita- 


ANIMALS. 


ble  driver  will  grow  poor,  while  with  kinder  treatment 
and  the  same  feed  and  work  he  might  maintain  a  good 
condition. 

It  is  true  of  the  lower  animals,  as  of  man,  that  "  it  is 
worry,  and  not  work,  that  kills."  Many  a  farmer  reduces 
the  income  from  his  stock  by  abusive  treatment. 

Conclusion,  —  A  knowledge  of  the  principles  of  agricul- 
ture is  simply  a  knowledge  of  some  of  the  laws  of  nature, 
which  have  a  divine  origin. 

To  understand  these  principles,  and  to  observe  them 
in  practice,  is  simply  to  place  ourselves  in  conformity 
with  natural  laws  which  are  based  upon  the  strictest  pro- 
priety and  economy. 

Success  and  failure  in  agriculture  turn  upon  this 
point.  The  heedless  and  indifferent  can  never  receive  so 
large  a  share  of  the  bounties  of  our  mother  Earth  as 
those  who  are  on  the  alert  to  catch  the  lessons  which 
nature  teaches,  and  to  profit  by  them.  "  If  ye  be  willing 
and  obedient,  ye  shall  eat  the  good  of  the  land." 

QUESTIONS. 

What  are  the  two  forms  of  life  ?  What  is  the  chief  purpose  of  vege- 
tation ?  Are,  the  bodies  of  animals  composed  of  the  same  materi- 
als as  plants?  What  is  the  difference  between  herbivorous  and 
carnivorous  animals?  What  is  the  nature  of  the  process  of  animal 
life? 

Name  the  different  classes  of  substances  in  the  body  of  an  animal. 
What  proportion  of  the  body  is  water  ?  What  is  the  use  of  water 
in  the  body?  What  parts  of  the  body  are  composed  of  nitrogenous 
substances?  Where  is  fat  to  be  found  in  the  body?  Explain 
the  different  kinds  of  fat.  What  elements  are  included  in  the 
"ash"? 

What  are  the  different  purposes  of  food  ?  What  use  do  young  ani- 
mals make  of  food  different  from  mature  animals  ?  Do  the  bodies 


142  THE   PRINCIPLES  OF  AGRICULTURE. 

of  mature  animals  remain  constantly  the  same?  What  is  the 
source  of  muscular  power  ?  How  is  animal  heat  supplied  by  food? 
At  what  temperature  must  the  body  be  kept  ?  How  is  it  cooled 
when  too  warm  in  hot  weather  ? 

Of  what  substances  is  food  composed  ?  Are  any  kinds  of  food  abso- 
lutely dry  ?  How  much  moisture  do  some  succulent  foods  contain  ? 
What  are  the  albuminoids  of  food  ?  What  parts  of  the  body  do 
they  form  ?  May  they  be  used  to  produce  heat  ?  Is  this  an  eco- 
nomical use  of  them  ?  Name  some  kinds  of  food  which  are  espe- 
cially rich  in  albuminoids.  Could  an  animal  live  entirely  upon 
albuminoids  ?  What  are  the  amides  ?  In  what  kinds  of  food  are 
they  chiefly  found?  How  do  they  differ  from  albuminoids ?  What 
is  protein  ?  What  uses  are  made  of  the  fats  of  food  ?  Why  can 
they  not  be  used  for  constructing  the  tissues  of  the  body  ?  Name 
some  of  the  different  kinds  of  fats.  -Name  some  articles  of  food 
which  are  rich  in  fats. 

What  are  the  carbo-hydrates  ?  Why  are  they  so  called  ?  What  use 
is  made  of  them  ?  How  valuable  are  they  ?  Could  an  animal  live 
entirely  upon  fats  and  carbo-hydrates  ?  Name  some  kinds  of  food 
which  are  largely  composed  of  carbo-hydrates.  Has  woody  fiber 
any  value  as  food  ? 

What  is  meant  by  the  "  ash  "  of  foods  ?  Of  what  substances  is  the 
ash  composed  ?  Are  these  substances  essential  in  the  food  of  ani- 
mals ?  Name  some  kinds  of  food  which  are  especially  rich  in 
albuminoids.  Name  some  in  which  the  fats  and  carbo-hydrates 
preponderate. 

Upon  what  does  the  value  of  food  depend  ?  Has  the  indigestible  part 
any  value?  Name  some  kinds  of  food  which  are  wholly  digestible. 
Name  some  kinds  of  which  a  large  part  is  indigestible. 

What  two  rules  should  be  generally  followed  in  feeding  stock  ?  Why 
should  animals  generally  be  fed  as  much  as  they  can  digest?  Is 
there  danger  in  feeding  too  much  ?  What  is  meant  by  a  "  balanced 
ration"?  Why  is  a  part  of  a  ration  that  is  not  well  balanced 
wasted  ? 

What  is  the  nutritive  ratio  of  a  food  ?  How  is  a  balanced  ration  made 
up  ?  Name  articles  of  food  which  might  be  combined  to  form  a 
proper  ration  for  oxen  at  work.  For  fattening  sheep.  What  is 
the  advantage  of  furnishing  a  variety  of  food  ? 

What  is  meant  by  the  "  manurial  value  "  of  food  ?     How  is  this  value 


ANIMALS.  143 

determined  ?  Is  the  manurial  value  of  the  same  variety  of  food 
always  the  same  ?  Are  the  manurial  substances  of  the  same  value 
in  whatever  food  they  are  found  ?  Name  articles  of  food  which 
have  a  high  manurial  value.  Wha  is  the  difference  between  the 
manurial  value  of  food,  and  the  value  of  the  manure  from  the  food  ? 
What  items  must  be  deducted  from  the  one  to  obtain  the  other? 
What  circumstances  increase  and  diminish  this  difference  ? 

What  are  the  two  values  of  food  ?  How  is  the  true  cost  of  food  to  be 
reckoned  in  farming  ?  Name  articles  which  cost  but  little  accord- 
ing to  this  method  of  reckoning. 

What  is  the  purpose  of  digestion  ?  Do  plants  digest  their  food,  like 
animals?  How  does  digestion  begin  in  the  mouth?  What  is  the 
saliva  ?  How  fast  is  it  formed  ?  Explain  the  action  of  the  stom- 
ach. Describe  the  intestines.  How  long  are  they  ?  What  becomes 
of  the  food  after  it  is  digested  ? 

Name  the  animals  called  "ruminants."  Why  is  their  digestive 
system  different  from  that  of  other  animals  ?  What  is  the  chief 
difference?  Describe  the  first  stomach.  WTiat  is  the  second 
stomach  ? 

What  service  does  the  third  stomach  perform?  Which  stomach 
corresponds  to  that  of  other  animals  ?  Into  which  stomach  does 
the  food  first  pass,  when  swallowed  ?  In  what  way  is  the  "  cud  " 
brought  to  the  mouth  ?  Into  which  stomach  does  it  pass  when 
swallowed  again  ?  What  may  be  the  difficulty  with  animals  unable 
to  chew  the  cud  ?  Why  are  ruminants  able  to  live  longer  without 
food  than  other  animals  ? 

What  is  the  use  of  the  blood  ?  In  which  parts  of  the  body  is  it  to  be 
found?  Describe  the  system  of  tubes  through  which  the  blood 
passes.  Why  does  it  pass  through  the  lungs  ?  Of  what  does  the 
blood  consist  ?  What  is  the  purpose  of  the  corpuscles  ?  From 
what  does  blood  derive  its  color  ?  Why  is  the  color  different  in 
different  parts  of  the  body  ? 

What  other  office  does  the  blood  fill  besides  conveying  nourishment 
to  the  body  ?  Name  the  other  waste  products  of  the  body  besides 
undigested  food.  Name  the  different  methods  by  which  they 
escape  from  the  body. 

How  does  an  animal  resemble  a  machine  ?  Why  is  one  animal  more 
profitable  than  another  for  a  given  purpose  ?  For  what  two  rea- 
sons should  the  health  of  animals  be  cared  for? 


144  THE  PRINCIPLES  OF  AGRICULTURE. 

What  is  the  origin  of  different  breeds  of  animals  ?  What  advantage 
is  there  in  thoroughbred  animals?  What  advantage  is  there  in 
a  variety  of  breeds  ?  Why  is  it  profitable  to  provide  shelter  for 
stock  ?  For  what  two  reasons  should  animals  receive  kind  treat- 
ment? How  does  unkind  treatment  reduce  the  income  from 
animals? 


GLOSSARY. 


Al-bu'mi-noids  .  .  A  class  of  substances  in  foods  which  contain  the 
most  of  the  nitrogen. 

Al'ka-li A  class  of  bases  including  ammonia,  soda,  potash. 

etc. 

Al'ka-line Resembling  or  possessing  the  qualities  of  the  al- 
kalies. 

Al-lu'vi-al Pertaining  to  a  river.  Alluvial  deposits  are  depos- 
its from  the  washing  of  rivers. 

Am'Ides A  class  of  substances  contained  in  foods. 

An-ti-cy'clone .  .  .  The  opposite  of  cyclone.  Winds  moving  in  the 
opposite  direction  from  those  of  a  neighboring 
storm,  or  cyclone. 

Ap'a-tite  ......     A  greenish  mineral  composed  of  phosphate  of  lime. 

As-sim'i-late  ....     To  convert  the  food  into  the  substances  of  the  body. 

Cal-ca're-ous    .  .  .     Consisting  of  lime,  or  containing  lime. 

Calyx The  outer  covering  of  a  flower. 

Cap'il-la-ries  ....  The  smallest  tubes  through  which  the  blood  passes 
in  its  circulation. 

Car-bo-hy'drates  .  A  large  class  of  substances  in  foods,  composed  of 
carbon,  hydrogen,  and  oxygen. 

Car-bo-na'ceous.  .     Containing  carbon,  or  composed  of  carbon. 

Car-iiiv'o-rous  .  .  .    Feeding  upon  the  flesh  of  animals. 

Cel'lu-lose A  substance  of  which  the  membranes  of  cells  of 

plants  are  largely  composed. 

Con-glom'er-ate .  .     Heaped  together. 

Co-rol'la The  inner  covering  of  a  flower. 

Cor'pus-cles  .  .  .  ,     Minute,  disk-shaped  particles,  floating  in  the  blood. 

Cot-y-le'don  ....  One  of  the  two  seed  leaves  of  a  plant  which  first 
appears. 

Cy'clone A  storm,  the  winds  of  which  blow  in  a  circuit. 

De-com-po-si'tion.  Decay,  or  a  chemical  change  into  other  substances. 

(145) 


146  GLOSSARY. 

Dis-in-te-gra'tion  .     Destruction,  or  separation  into  parts. 
Ex-crS'tion Throwing   off   useless  matter    from    the  animal 

system. 

Gla'cier An  immense  mass  of  moving  ice. 

Her-biv'o-rous    .  .     Eating  herbs.     Living  upon  vegetation. 

Hu'mus A  dark  or  brown  substance,  common  in  soils. 

In  com-bus'ti-ble  .    Not  capable  of  being  burned. 

I'so-bar A  line  indicating  the  points  where  the  height  of  the 

barometer  is  the  same. 
Is o  therm   .....    A  line  indicating  points  where  the  temperature  is 

the  same. 
Lac'te-als  ......     Passages  through  which  blood  is  conveyed  from 

the  stomach  and  intestines  to  the  blood-vessels. 
Le-gu'mi-nous  .  .        Pertaining  to  a  class  of  plants,   including  peas, 

beans,  clover,  etc. 
Ni-tri-fi-ca'tion  .  .     A  natural  process  by  which  nitrates  are  formed  14 

the  soil. 
Ni-trog'e-nous  .  .  ,     Pertaining  to  nitrogen,  or  containing  nitrogen. 

O'le-in The  oily  part  of  foods  in  the  animal  body. 

Pal'mi-tin One  of  the  kinds  of  animal  fat. 

Pet'ri-fied Converted  into  stone,  or  into  a  substance  like  stone. 

Plu'mule The  first  bud,  or  ascending  part  of  a  young  plant. 

Pro'te-in Those  parts  of  food  which  furnish  nitrogen. 

Ru'mi-nate  .....    To  chew  the  cud. 
Ru'mi-nant    ....     An  animal  that  chews  the  cud, 

SaTi-va-ry Producing  saliva. 

Se-crete' To  separate ;  as  to  separate  fluids  from  the  blood. 

Ste'a-rin One  of  the  hard  kinds  of  fat  in  the  animal  body. 

Sto'ma-ta Minute  mouths  or  openings   on  the   surface  of 

leaves. 

Tu'ber-ous Covered  with  or  containing  tubers. 

U're-a  .  .  .  ,  .  .  .        One  of  the  waste  substances  of  the  system,  sepa- 
rated from  the  blood  by  the  kidneys. 


INDEX. 


PAGE 

Absorbing  power  of  roots  ...      68 

Absorption,  of  water  by  plants  .      62 

of  ammonia  bv  plants     .     .      62 

Acids      .     .     .     ." 12 

Acids,  bases,  and  salts  ....      12 

Adhesion 14 

Age  of  the  earth 27 

Agriculture,  effect  of    ....      78 

Air,  composition  of 41 

necessary  for  roots      .     .     .     101 
purified  by  plants  ....      61 

Albuminoids 118 

Alkalies 13 

Alum 17 

Alumina 23 

Aluminium 23 

Alluvial  soil 32 

Amides 119 

Ammonia     ....       11,  13,  18,  21 
absorbed  by  foliage     ...      62 

carbonate  of 82 

formation  of       ....      81,  82 

Ammonic  chloride 13 

Animal  heat 117,140 

Animals,  remains  of      ....       37 

breeds  of 139,  140 

care  of 140 

composition  of  bodies  of.     .     114 

health  of 138 

kindness  to 140 

nature  of 138 

young ...     ,,     ....     116 

Apatite 85 

Application  of  fertilizers    ...      89 
Application  of  manure  ....      94 

Arteries,  the 136,  137 

Artificial  fertilizers 83 


PACK 
Ash  of  animal  bodies  ....  116 

of  food 120 

Atmosphere 31,  41 

weight  of 42 

Atomic  theory 8 

Atoms 8,  11 


Balanced  ration    ....      124,  125 

Barometer 43,  44 

Bases 12,  13 

Beans 62 

Beets 63 

Biennial  plants 62 

Blight 69 

Blood,  the 136,  137,  138 

Blue  litmus 66 

Bodies  of  animals    .    .    114,  115,  116 

Bones  as  a  fertilizer 84 

Bone-black 84 

Bowlders,  origin  of 34 

Breathing 137 

of  plants 61,  62 

Breeds  of  animals    .     .     .      139,  140 

Breezes 45 

Brimstone 24 

Buttercups,  roots  of 63 


Calcareous  soil 39 

Calcium 23 

carbonate 23 

hydrate 86 

oxide 19,86 

phosphate 22 

Calyx 74 

(147) 


148 


INDEX. 


PAGE 

Canada  thistles 63 

Cane  sugar 12 

Cap  of  roots 64 

Capillaries,  the 137 

Capillary  attraction 67 

of  roots 68 

in  plants 71 

Carbo-hydrates    ....      119,  120 

Carbon 21 

from  the  air 60,  61 

Carbonate  of  ammonia      ...      82 

Carbon  dioxide 19 

Carbonic  acid  .  13,  14,  18,  19,  20,  41 
absorbed  by  plants  ...  61 
in  the  animal  system  .  .  .  138 

in  the  soil 101 

Carboniferous  vegetation  ...      39 

Care  of  animals 140 

Carnivorous  animals     ....    114 

Carrots 63 

Caustic  potash 23 

Caustic  soda 23 

Cells 68 

form  of 70 

growth  of 69 

of  a  potato 69 

of  ripe  fruit 69 

Cellulose 60 

Charcoal 21 

as  a  filter 14 

Chemical  action 11 

in  soil       80 

Chemical  affinity 9 

Chemical  equations 12 

Chemicals,  use  of 88 

Chewing  the  cud     ....  135,  136 

Chlorate  of  potash 23 

Chloride  of  potash     .     .     .     .     13,  85 

Chlorine 22 

Circulation  of  the  blood     ...    136 

Clay 22 

Clayey  soil 38 

Climate 50,  51 

Clouds 47 

Clover 62,  63,  73 

roots 64 

Coal,  origin  of 37 

Cohesion 14 

Cold  wave 49 

Combustible  matter 18 


PAGE 

Combustion 20 

Composition  of  foods     ....  118 

of  soil 77 

Continents,  formation  of   ...  27 

Cooling  of  the  body      ....  118 

Coral  reefs  .     .     . " 37 

Corn  meal,  effects  of     ....  120 

Corpuscles 138 

Cotton 70 

fiber 73 

Cranberry  plants 101 

Crops,  rotation  of 110 

Crystallizing 19 

Crystals  of  snow 17 

Cultivation 100 

deep 107 

of  hoed  crops 107 

purposes  of 100-103 

shallow 107 


D. 

Dark  weather,  effect  of     ...  61 

Decomposition 20 

of  soil 101 

Deep  cultivation 107 

Deep  plowing 104 

Dew 48 

Diamonds 21 

Diffusion 65 

in  plants 68,  72 

Digestible  parts  of  food     .    .    .  121 

Digestion 133 

Disks  of  the  blood 138 

Drainage,  by  deep  tillage  .     .     .  104 

Draining 108 

cold  soil 110 

Drains,    to    prevent    effect    of 

drought 109 


Earth,  its  original  condition  .     .  26 

its  age 29 

its  interior 26 

Earthquakes 26 

Economy  in  feeding .     .     .      122,  123 

Effect  of  agriculture      ....  78 

Effervescence 14 

Elementary  substances      ...  8 


INDEX. 


149 


PAGE 
Equations,  chemical      ....      12 

Erigenia 63 

Evaporation  from  soil   ....     110 

Excretion 138 

Exposure  of  manure      ....      94 

F. 

Farm,  care  of 92 

Farm  manure 90 

nature  of 90,  91 

Fat,  animal 115 

in  food 119 

varieties  of    ....      115,  116 

Feed,  true  cost  of 132 

Fermentation  of  manure    ...      92 

Fertile  soil 77 

Fertility 37 

maintained 79 

reduced  by  weeds  ....     102 

Fertilizers 77 

artificial 83 

prepared 85 

Fiber  in  foods 120 

of  wood 70 

Fibrous  roots 63 

Flow  of  sap 65,  72 

Flowers 73 

Fogs 47 

Food  of  plants 60,  65 

Food,  purposes  of  ...  116,  117 
digestible  parts  of  ....  122 
quantity  profitable  .  .  .  124 

variety  of 129 

Foods,  composition  of  .  .  118,  121 
double  value  of  ...  131,  132 
manurial  value  of  .  .  129,  130 

true  cost  of 132 

value  of 122 


G. 

Germ  of  seeds 54 

Germination 57 

Glaciers 34 

Glands,  salivary 133 

Glass 22 

Granite 22 

soil  from 79 

Graphite 23 


PAGE 

Gravelly  soil 38 

Growth,  of  roots 63 

of  plants  ......     68,  69 

Guano 85 

Gullet,  the 135 

Gum  arabic     .......      12 

Gypsum 13,  87,  88 


Hail 47 

Hard  pan 31 

Harrowing,  purposes  of     ...  106 

thorough 106 

Health  of  animals 139 

Heat,  effect  of 16 

animal 117 

in  germination 58 

Herbivorous  animals    ....  114 

Hills 32 

formation  of 29,  30 

worn  away  by  winds  ...  35 

Hoed  crops,  cultivation  of      .    .  107 

Humus 35 

Hydrochloric  acid    .     .     .     11-13, 22 

Hydrogen 20 


Ice,  effect  of,  upon  soil ....  32 

Impurities  of  the  atmosphere  .  42 

Indian  corn,  roots  of  ....  64 

mixture  of 74 

Insects,  avoided  by  rotation  .  .  112 

Intestines,  the 133 

length  of 133 

Iron 125 


Kidneys,  the 
Kindness  to  animals 


138 
140 


Lacteals,  the 134 

Leguminous  plants 62 

Lime 12,  13,  19,  41,  86 

benefit  of,  in  soil    ....      87 
Limestone 23,  32,  37 


150 


INDEX. 


PAGE 

Limestone,  soil  from     ....  79 

Limy  soil 41 

Liquid  manure 94 

Litmus 66 

Loam 39 

Lucerne      ........  62 

Lungs,  the 138 


Magnesia 13,  23 

Manure 90 

application  of 94 

fermentation  of 92 

from  foods,  value  of   ...     131 

losses  of 92,  93,  94 

Manurial  value  of  foods  129,  130,  131 

Marble 23,  31 

Marl 87 

Mastication 133 

Matter,  nature  of 10 

Mist 47 

Moisture  of  climate  ....  51,  52 
in  germination  ....  55,  58 
regulated  by  cultivation  .  103 
withdrawn  by  weeds  .  .  .  102 

Mold,  vegetable 79 

Molecules 9 

Mountains 29,  32 

formation  of 27 

Mouth,  the 133 

Mouths  of  leaves 61 

Muck 95,  96 

value  of 96,  97 

Muck  beds 35 

Mucky  soil 39 

Muriate  of  potash 85 

Muriatic  acid 13,  22 


N. 
Nitrate  of  lime 82 

of  potash 82 

of  soda 13,  82,  84 

Nitrates 82 

in  soil 81 

Nitric  acid 13 

in  soil 81,  82 

Nitrification 82,  83 

Nitrogen    ...       20,  41,  62,  81,  84 


PAGE 

Nitrogen  as  food  for  plants     .    .       62 
North  America,  formation  of      .      27 

Nutrition  in  plants 72 

Nutritive  ratio      ....      124,  126 

O. 

Oak  trees,  roots  of 63 

Ocean,  affecting  climate    ...      51 

soil  formed  by 32 

Organic  matter 17,  18 

Osmose 62 

in  plants 71 

Oxidation 19,  20 

of  plants 62 

Oxide  of  iron 13 

Oxides 19 

Oxygen 19, 20 

in  germination  of  plants       .       56 

in  soil 101 

in  the  blood 61 


P. 

Paunch,  the 134 

Peas 62 

Peat 35,  37 

Peaty  soil 35,  39 

Perspiration,  effect  of    ....     118 

Petals 74 

Phosphate  of  lime    ....     13,  84 
Phosphoric  acid        .     .   13,  22,  83,  84 

Phosphorus 22 

Pistils 74 

Planting,  depth  of 57 

Plants,  growth  of 68 

breathing  of 20 

food  of 60 

instinct  of 59 

leguminous 62 

structure  of 68 

Plant  food,  formation  of    .     .     .     101 

Plaster,  land 87 

Plowing 103,104 

subsoil 105 

time  for 105,  106 

Plumule,  the 59 

Pores  of  wood 15 

Porosity  of  matter 15 

Potassium 23 


INDEX. 


151 


PAGE 

Potash 23,  83,  85 

salts 85 

Potato,  cells  of 69 

Prepared  fertilizers  ....     85,  86 

Pressure  of  the  air 43 

Protein 118,119 


Q- 

Quartz  rock 22 

Quicklime 13,  86 


Radicle,  the 59,  62,  63 

Rain 42.  45,  46,  47 

Rainless  regions 47 

Rain  water,  a  fertilizer      .     .     .     108 

Ratio,  nutritive 125 

Ration,  balanced 125 

Rations,  how  made  up  .     .     .     .     J27 

examples  of 128, 129 

Requirements  of  animals  .     .     .     127 

Respiration 20 

Rice  plants 101 

Rochelle  powders 13 

Rocks,  ancient 30 

RoHingland 107 

Rootlets 64 

Roots      . 63,  64 

air  necessary  for     ....     101 

in  wet  soil 108 

of  buttercups 63 

of  clover 64 

of  the  maple 63 

tap 63 

tuberous 63 

Rotation  of  crops       .     .     .     .110-112 

Ruminants 1 '34-136 

stomachs  of 134,135 

Running  water,  effect  of    ...      31 
"Runout"  land      .     .  79 


Saliva j.)3 

Salivary  glands ];j;j 

Salt 11,  12,  17,  65,  87 

Saltpeter 84 

Sandstone „     22,  31,  32 


PAGE 

Sandy  soil 37,  38,  105 

Sap  of  plants 65 

flow  of 71,  72 

Saturated  soil 101 

Sea  breezes 45 

Seeds 54 

unripe 55 

Selection  of  food  by  plants     .     .      73 

Sepals 74 

Shallow  cultivation  .....     107 

Silicates 22 

Silicon 22,73 

Silicic  acid 13 

Simple  substances 7 

Slag 85 

Slaked  lime 12 

Smoked  glass 21 

Smut 69 

Snow 47 

crystals 17 

Sodium 13,  23 

Soil,  formation  of     ....     27,  30 

alluvial 105 

composition  of   ...    3^,  35,  78 

fertile  .  77 

from  granite 79 

from  limestone 79 

sandy 37,  38.  105 

warmth  of 110 

Solids,  liquids,  and  gases  ...  16 
South  Carolina  rock  ....  85 
Squashes,  mixture  of  ....  74 

Stamens 74 

Starch 60 

of  potatoes 69 

Stomach,  the 133,  134 

Stomachs  of  ruminants      .     .     .135 

Stomata 60,  61 

Storms 50 

Subsoil 104 

plowing 105 

Substances,  simple 7 

Success  in  agriculture   .     .     .     .     141 

Sugar 13,  60 

Sulphates 13,84 

Sulphate  of  ammonia    .     ,     .     .      84 
of  lime      .......       13 

of  potash 23 

Sulphur 22 

Sulphuric  acid      .     ,  10,  13,  21,  22,  66 


152 


INDEX. 


PAGE 

Summer  fallowing 101 

Sunlight,  effect  of 62 


T. 

Tap-roots 63 

Temperature 44,  50 

Thermometer 44 

Tillage,  deep 104 

Time  to  plow 105 

Timothy  grass 73 

Tuberous  roots 63 

Turnips 63 


U. 


Underdrains 
Unripe  seeds 
Urea  .  . 


108 

55 

138 


V. 

Valleys,  cause  of 30 

Value  of  foods 121, 122 

Variety  of  food 129 

Vegetable  matter 35 

Vegetable  mold        .     .     .     .     35,  79 

Vegetable  tissue 69 

Vegetation,  carboniferous      .     .      36 
Veins,  the 137 


PAGE 

Vitality  of  seeds 54 

Volatile  substances 21 


W. 

Warm  wave 49 

Warmth  for  germination    ...  50 

Water,  magnified 9 

in  foods 118 

in  the  animal  body      .     .     .  115 

molecule 11 

vapor 41 

Watering  plants 62 

Weather,  the 49 

Weeds 102 

Wetland 109 

White  clover 63 

Wind 34,  35,  44,  45 

Wood,  composition  of   ....  7 

Wood,  porosity  of 15 

Work,  effect  of 117 


Y. 

Young  animals 116 


Zinc '  .     .     .     11,  12 

Zinc  chloride 12 


Standard  Text- Books  in  Botany 


Clark's  Laboratory  Manual  in  Practical  Botany          .         .         .     $0.96 
For  Secondary  Schools  and  Elementary  College  work. 

Gray's  How  Plants  Behave 54 

For  Beginners  in  Primary  Schools. 

Gray's  How  Plants  Grow  ". 80 

For  Intermediate  and  Grammar  Schools. 
Gray's  School  and  Field  Book  of  Botany 1.80 

The  Standard  Text-Book  for  High  Schools,  Academies,  etc. 
Gray's  Lessons  in  Botany.     (Revised)  .....         .94 

Gray's  Field,  Forest  and  Garden  Botany.     (Flora)       .         .         .1.44 
Gray's  Lessons  and  Manual.     (In  one  volume)       ....       2.16 

For  Advanced  Students,  Teachers,  and  Practical  Botanists. 
Gray's  Manual  of  Botany.     (Flora)       .  ....       1.62 

Coulter's  Botany  of  the  Rocky  Mountains  .         .         .         .1.62 

A  flora  adapted  to  the  mountain  section  of  the  United  States. 
Gray  and  Coulter's  Text-Book  of  Western  Botany     .         .         .       2.16 
Being  Gray's  Lessons  and  Coulter's  Manual  bound  in  one  volume. 

Gray's  Structural  Botany 2.00 

Goodale's  Physiological   Botany 2.00 

Dana's  Plants  and  their  Children        ......         .65 

Herrick's  Chapters  on   Plant  Life 60 

Steele's  Fourteen  Weeks  in  Botany 1.00 

Wood's  How  to  Study  Plants 1.00 

Same  as  Steele's  Fourteen  Weeks  in  Botany,  with  added  chapters  on 
Physiological  and  Systematic  Botany. 

Wood's  Lessons  in  Botany.     (Revised)         .....         .90 

Wood's  New  American  Botanist  and  Florist.     (Revised)       .         .       1.75 
Wood's  Descriptive  Botany         .         .         .         .         .         .         .1.25 

Being  the  flora  of  the  New  American  Botanist  and  Florist. 

Wood's  Class  Book  of  Botany 2.50 

A  standard  work  for  Advanced  Classes  and  for  the  Student's  Library. 

Youmans's  First  Book  in  Botany 64 

Youmans's  Descriptive  Botany    .         .         .         .         .         .         .1.20 

Bentley's  Physiological  Botany  . 1.20 

A  sequel  to  Youmans's  Descriptive  Botany. 

Willis's  Practical  Flora 1.50 

A  valuable  supplementary  aid  to  any  text-book  in  the  study  of  Botany. 


Copies  of  any' of  the  above  books  will  be  sent,  prepaid,  to  any  address  on 
receipt  of  the  price  by  the  Publishers: 

American   Book   Company 

NEW  YORK  *  CINCINNATI  »  CHICAGO 

(100) 


School  Histories  of  the  United  States 


McMaster's  School   History  of  the   United   States 

By  JOHN   BACH   MCMASTER.       Cloth,    i2tno,   507   pages. 

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UNIVERSITY   OF    CALIFORNIA 
LIBRARY 

This  is  the  date  on  which  this 
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[30m-6,'ll] 


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